diff --git a/.clang-tidy b/.clang-tidy
index fc4fd05fa1b..f3a73ec0e10 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -40,7 +40,6 @@ Checks: >
        -modernize-return-braced-init-list,
        -modernize-use-constraints,
        -modernize-use-designated-initializers,
-       -modernize-use-integer-sign-comparison,
        -modernize-use-ranges,
        -modernize-use-starts-ends-with,
        -modernize-use-std-numbers,
@@ -82,5 +81,4 @@ HeaderFileExtensions: ['', "H", 'h', 'hh', 'hpp', 'hxx']
 # -modernize-use-designated-initializers
 # -modernize-use-std-numbers
 # -modernize-use-ranges
-# -modernize-use-integer-sign-comparison
 # -modernize-use-starts-ends-with
diff --git a/Src/Amr/AMReX_AmrLevel.cpp b/Src/Amr/AMReX_AmrLevel.cpp
index 156ff8caeaa..8db4ae21e9b 100644
--- a/Src/Amr/AMReX_AmrLevel.cpp
+++ b/Src/Amr/AMReX_AmrLevel.cpp
@@ -16,6 +16,7 @@
 #endif
 
 #include <sstream>
+#include <iterator>
 #include <memory>
 #include <limits>
 
@@ -108,7 +109,7 @@ AmrLevel::AmrLevel (Amr&            papa,
     }
 
     // Note that this creates a distribution map associated with grids.
-    for (int i = 0; i < state.size(); i++)
+    for (int i = 0; i < std::ssize(state); i++)
     {
         MultiFab::RegionTag statedata_tag("StateData_Level_" + std::to_string(lev));
         MultiFab::RegionTag statedata_index_tag("StateData_" + std::to_string(i) + "_Level_" + std::to_string(lev));
@@ -143,7 +144,7 @@ AmrLevel::writePlotFile (const std::string& dir,
     // second component of pair is component # within the state_type
     //
     std::vector<std::pair<int,int> > plot_var_map;
-    for (int typ = 0; typ < desc_lst.size(); typ++)
+    for (int typ = 0; typ < std::ssize(desc_lst); typ++)
     {
         for (int comp = 0; comp < desc_lst[typ].nComp();comp++)
         {
@@ -197,7 +198,7 @@ AmrLevel::writePlotFile (const std::string& dir,
         //
         // Names of variables
         //
-        for (i =0; i < static_cast<int>(plot_var_map.size()); i++)
+        for (i =0; i < std::ssize(plot_var_map); i++)
         {
             int typ = plot_var_map[i].first;
             int comp = plot_var_map[i].second;
@@ -286,7 +287,7 @@ AmrLevel::writePlotFile (const std::string& dir,
         os << level << ' ' << grids.size() << ' ' << cur_time << '\n';
         os << parent->levelSteps(level) << '\n';
 
-        for (i = 0; i < grids.size(); ++i)
+        for (i = 0; i < std::ssize(grids); ++i)
         {
             RealBox gridloc = RealBox(grids[i],geom.CellSize(),geom.ProbLo());
             for (n = 0; n < AMREX_SPACEDIM; n++) {
@@ -326,7 +327,7 @@ AmrLevel::writePlotFile (const std::string& dir,
     //
     // Cull data from state variables -- use no ghost cells.
     //
-    for (i = 0; i < static_cast<int>(plot_var_map.size()); i++)
+    for (i = 0; i < std::ssize(plot_var_map); i++)
     {
         int typ  = plot_var_map[i].first;
         int comp = plot_var_map[i].second;
@@ -477,7 +478,7 @@ AmrLevel::setTimeLevel (Real time,
                         Real dt_old,
                         Real dt_new)
 {
-    for (int k = 0; k < desc_lst.size(); k++)
+    for (int k = 0; k < std::ssize(desc_lst); k++)
     {
         state[k].setTimeLevel(time,dt_old,dt_new);
     }
@@ -486,7 +487,7 @@ AmrLevel::setTimeLevel (Real time,
 bool
 AmrLevel::isStateVariable (const std::string& name, int& state_indx, int& n)
 {
-    for (state_indx = 0; state_indx < desc_lst.size(); state_indx++)
+    for (state_indx = 0; state_indx < std::ssize(desc_lst); state_indx++)
     {
         const StateDescriptor& desc = desc_lst[state_indx];
 
@@ -577,7 +578,7 @@ AmrLevel::~AmrLevel ()
 void
 AmrLevel::allocOldData ()
 {
-    for (int i = 0; i < desc_lst.size(); i++)
+    for (int i = 0; i < std::ssize(desc_lst); i++)
     {
         state[i].allocOldData();
     }
@@ -586,7 +587,7 @@ AmrLevel::allocOldData ()
 void
 AmrLevel::removeOldData ()
 {
-    for (int i = 0; i < desc_lst.size(); i++)
+    for (int i = 0; i < std::ssize(desc_lst); i++)
     {
         state[i].removeOldData();
     }
@@ -595,7 +596,7 @@ AmrLevel::removeOldData ()
 void
 AmrLevel::reset ()
 {
-    for (int i = 0; i < desc_lst.size(); i++)
+    for (int i = 0; i < std::ssize(desc_lst); i++)
     {
         state[i].reset();
     }
@@ -1013,7 +1014,7 @@ FillPatchIterator::Initialize (int  boxGrow,
     const IndexType& boxType = m_leveldata->boxArray().ixType();
     const int level = m_amrlevel->level;
 
-    for (int i = 0, DComp = 0; i < static_cast<int>(m_range.size()); i++)
+    for (int i = 0, DComp = 0; i < std::ssize(m_range); i++)
     {
         const int SComp = m_range[i].first;
         const int NComp = m_range[i].second;
diff --git a/Src/Base/AMReX.cpp b/Src/Base/AMReX.cpp
index 93529d623a8..05c49663494 100644
--- a/Src/Base/AMReX.cpp
+++ b/Src/Base/AMReX.cpp
@@ -59,6 +59,8 @@
 #include <AMReX_MemProfiler.H>
 #endif
 
+#include <iterator>
+
 #ifdef AMREX_USE_OMP
 #include <AMReX_OpenMP.H>
 #include <omp.h>
@@ -979,7 +981,7 @@ amrex::command_argument_count ()
 std::string
 amrex::get_command_argument (int number)
 {
-    if (number < static_cast<int>(command_arguments.size())) {
+    if (number < std::ssize(command_arguments)) {
         return command_arguments[number];
     } else {
         return std::string();
diff --git a/Src/Base/AMReX_CArena.cpp b/Src/Base/AMReX_CArena.cpp
index ed8be19d7d9..2f31753c07a 100644
--- a/Src/Base/AMReX_CArena.cpp
+++ b/Src/Base/AMReX_CArena.cpp
@@ -37,7 +37,7 @@ void*
 CArena::alloc_protected (std::size_t nbytes)
 {
     bool freeunused_called = false;
-    if (static_cast<Long>(m_used+nbytes) >= arena_info.release_threshold) {
+    if (std::cmp_greater_equal(m_used+nbytes, arena_info.release_threshold)) {
         freeUnused_protected();
         freeunused_called = true;
     }
diff --git a/Src/Base/AMReX_DistributionMapping.cpp b/Src/Base/AMReX_DistributionMapping.cpp
index e88cc0c3597..d6b8d03bb2e 100644
--- a/Src/Base/AMReX_DistributionMapping.cpp
+++ b/Src/Base/AMReX_DistributionMapping.cpp
@@ -22,6 +22,8 @@
 #include <string>
 #include <cstring>
 #include <iomanip>
+#include <iterator>
+#include <utility>
 
 namespace {
     int flag_verbose_mapper;
@@ -177,7 +179,7 @@ void
 DistributionMapping::Sort (std::vector<LIpair>& vec,
                            bool                 reverse)
 {
-    if (vec.size() > 1)
+    if (std::ssize(vec) > 1)
     {
         if (reverse) {
             std::stable_sort(vec.begin(), vec.end(), LIpairGT());
@@ -422,7 +424,7 @@ DistributionMapping::RoundRobinDoIt (int                  nboxes,
 
     if (LIpairV)
     {
-        BL_ASSERT(static_cast<int>(LIpairV->size()) == nboxes);
+        BL_ASSERT(std::ssize(*LIpairV) == nboxes);
 
         for (int i = 0; i < nboxes; ++i)
         {
@@ -766,7 +768,7 @@ DistributionMapping::KnapSackDoIt (const std::vector<Long>& wgts,
         }
     }
 
-    BL_ASSERT(static_cast<int>(vec.size()) == nteams);
+    BL_ASSERT(std::ssize(vec) == nteams);
 
     std::vector<LIpair> LIpairV;
 
@@ -864,7 +866,7 @@ DistributionMapping::KnapSackProcessorMap (const std::vector<Long>& wgts,
     m_ref->clear();
     m_ref->m_pmap.resize(wgts.size());
 
-    if (static_cast<int>(wgts.size()) <= nprocs || nprocs < 2)
+    if (std::ssize(wgts) <= nprocs || nprocs < 2)
     {
         RoundRobinProcessorMap(static_cast<int>(wgts.size()),nprocs, sort);
 
@@ -894,7 +896,7 @@ DistributionMapping::KnapSackProcessorMap (const DistributionMapping& olddm,
 
     ComputeDistributionMappingEfficiency(olddm, wgts, &old_efficiency);
 
-    if (static_cast<int>(wgts.size()) <= nprocs || nprocs < 2)
+    if (std::ssize(wgts) <= nprocs || nprocs < 2)
     {
         RoundRobinProcessorMap(static_cast<int>(wgts.size()),nprocs, false);
         new_efficiency = Real(1);
@@ -927,7 +929,7 @@ DistributionMapping::KnapSackProcessorMap (const DistributionMapping& olddm,
                     w += wi;
                 }
             }
-            if (i < static_cast<int>(kb.size())) {
+            if (i < std::ssize(kb)) {
                 lb.insert(lb.end(), kb.begin()+i, kb.end());
                 kb.erase (          kb.begin()+i, kb.end());
             }
@@ -990,7 +992,7 @@ DistributionMapping::KnapSackProcessorMap (const DistributionMapping& olddm,
             AMREX_ASSERT(max_weight > Real(0));
             new_efficiency = avg_weight / max_weight;
 
-            if (new_efficiency < max_efficiency && wblv.size() > 1) {
+            if (new_efficiency < max_efficiency && std::ssize(wblv) > 1) {
                 BL_PROFILE("knapsack()swap");
 
                 std::sort(wblv.begin(), wblv.end());
@@ -1207,7 +1209,7 @@ Distribute (const std::vector<SFCToken>&     tokens,
         }
     }
 
-    BL_ASSERT(static_cast<int>(v.size()) == nprocs);
+    BL_ASSERT(std::ssize(v) == nprocs);
 
     int  K        = 0;
     Real totalvol = 0;
@@ -1502,7 +1504,7 @@ DistributionMapping::SFCProcessorMap (const BoxArray&          boxes,
                                       bool                     sort)
 {
     BL_ASSERT( ! boxes.empty());
-    BL_ASSERT(boxes.size() == static_cast<int>(wgts.size()));
+    BL_ASSERT(boxes.size() == std::ssize(wgts));
 
     m_ref->clear();
     m_ref->m_pmap.resize(wgts.size());
@@ -1525,7 +1527,7 @@ DistributionMapping::SFCProcessorMap (const BoxArray&          boxes,
                                       bool                     sort)
 {
     BL_ASSERT( ! boxes.empty());
-    BL_ASSERT(boxes.size() == static_cast<int>(wgts.size()));
+    BL_ASSERT(boxes.size() == std::ssize(wgts));
 
     m_ref->clear();
     m_ref->m_pmap.resize(wgts.size());
@@ -1948,7 +1950,7 @@ operator<< (std::ostream&              os,
 {
     os << "(DistributionMapping" << '\n';
 
-    for (int i = 0; i < pmap.ProcessorMap().size(); ++i)
+    for (int i = 0; i < std::ssize(pmap.ProcessorMap()); ++i)
     {
         os << "m_pmap[" << i << "] = " << pmap.ProcessorMap()[i] << '\n';
     }
@@ -2018,7 +2020,7 @@ DistributionMapping MakeSimilarDM (const BoxArray& ba, const BoxArray& src_ba,
                               "input BoxArrays must have the same centering.");
 
     Vector<int> pmap(ba.size());
-    for (int i = 0; i < static_cast<int>(ba.size()); ++i) {
+    for (int i = 0; i < std::ssize(ba); ++i) {
         Box box = ba[i];
         box.grow(ng);
         bool first_only = false;
diff --git a/Src/Base/AMReX_FabArray.H b/Src/Base/AMReX_FabArray.H
index 3186ae4276b..8114eadbfb1 100644
--- a/Src/Base/AMReX_FabArray.H
+++ b/Src/Base/AMReX_FabArray.H
@@ -43,6 +43,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <iterator>
 #include <limits>
 #include <map>
 #include <memory>
@@ -1755,7 +1756,7 @@ bool
 FabArray<FAB>::defined (int K) const noexcept
 {
     int li = localindex(K);
-    if (li >= 0 && li < static_cast<int>(m_fabs_v.size()) && m_fabs_v[li] != 0) {
+    if (li >= 0 && li < std::ssize(m_fabs_v) && m_fabs_v[li] != 0) {
         return true;
     }
     else {
@@ -1768,7 +1769,7 @@ bool
 FabArray<FAB>::defined (const MFIter& mfi) const noexcept
 {
     int li = mfi.LocalIndex();
-    if (li < static_cast<int>(m_fabs_v.size()) && m_fabs_v[li] != nullptr) {
+    if (li < std::ssize(m_fabs_v) && m_fabs_v[li] != nullptr) {
         return true;
     }
     else {
@@ -1874,7 +1875,7 @@ FAB*
 FabArray<FAB>::release (int K)
 {
     const int li = localindex(K);
-    if (li >= 0 && li < static_cast<int>(m_fabs_v.size()) && m_fabs_v[li] != nullptr) {
+    if (li >= 0 && li < std::ssize(m_fabs_v) && m_fabs_v[li] != nullptr) {
         AMREX_ASSERT(m_single_chunk_arena == nullptr);
         Long nbytes = amrex::nBytesOwned(*m_fabs_v[li]);
         if (nbytes > 0) {
@@ -1894,7 +1895,7 @@ FAB*
 FabArray<FAB>::release (const MFIter& mfi)
 {
     const int li = mfi.LocalIndex();
-    if (li >= 0 && li < static_cast<int>(m_fabs_v.size()) && m_fabs_v[li] != nullptr) {
+    if (li >= 0 && li < std::ssize(m_fabs_v) && m_fabs_v[li] != nullptr) {
         AMREX_ASSERT(m_single_chunk_arena == nullptr);
         Long nbytes = amrex::nBytesOwned(*m_fabs_v[li]);
         if (nbytes > 0) {
diff --git a/Src/Base/AMReX_FabConv.cpp b/Src/Base/AMReX_FabConv.cpp
index f07bbed2279..607f1b1e7b5 100644
--- a/Src/Base/AMReX_FabConv.cpp
+++ b/Src/Base/AMReX_FabConv.cpp
@@ -770,7 +770,7 @@ PD_fconvert (void*       out,
         for (i = 0L; i < nitems; i++, rout += outbytes)
         {
             for (j = 0; j < outbytes; j++) {
-                if ((j == indxout) ? (rout[j] != mask) : rout[j]) {
+                if ((j == indxout) ? std::cmp_not_equal(rout[j], mask) : rout[j]) {
                     break;
                 }
             }
diff --git a/Src/Base/AMReX_GpuDevice.cpp b/Src/Base/AMReX_GpuDevice.cpp
index 1e5423bdb80..1043349cd86 100644
--- a/Src/Base/AMReX_GpuDevice.cpp
+++ b/Src/Base/AMReX_GpuDevice.cpp
@@ -12,11 +12,12 @@
 #endif
 
 #include <iostream>
-#include <map>
 #include <algorithm>
+#include <exception>
+#include <iterator>
+#include <map>
 #include <string>
 #include <unordered_set>
-#include <exception>
 
 #if defined(AMREX_USE_CUDA)
 #include <cuda_profiler_api.h>
@@ -758,7 +759,7 @@ Device::setStream (gpuStream_t s) noexcept
         }
     }
     int const idx = streamIndex(s);
-    if (idx == static_cast<int>(gpu_stream_pool.size())) {
+    if (idx == std::ssize(gpu_stream_pool)) {
         amrex::Abort("Gpu::Device::setStream: stream is not managed by AMReX.");
     }
     gpu_stream_index[tid] = idx;
diff --git a/Src/Base/AMReX_NFiles.cpp b/Src/Base/AMReX_NFiles.cpp
index fd8e5fef60c..f5107ee2c3a 100644
--- a/Src/Base/AMReX_NFiles.cpp
+++ b/Src/Base/AMReX_NFiles.cpp
@@ -1,6 +1,7 @@
 
 #include <AMReX_NFiles.H>
 #include <deque>
+#include <iterator>
 #include <set>
 #include <utility>
 
@@ -504,7 +505,7 @@ bool NFilesIter::CheckNFiles(int nProcs, int nOutFiles, bool groupSets)
     }
 //    amrex::Print() << "nOutFiles fileNumbers.size() = " << nOutFiles
 //              << "  " << fileNumbers.size() << '\n';
-    if(nOutFiles != static_cast<int>(fileNumbers.size())) {
+    if(nOutFiles != std::ssize(fileNumbers)) {
 //      amrex::Print() << "**** Different number of files." << '\n';
       return false;
     }
@@ -529,7 +530,7 @@ Vector<int> NFilesIter::FileNumbersWritten()
         procSet.insert(fileNumbersWriteOrder[f][r]);
       }
     }
-    if(total != nProcs || static_cast<int>(procSet.size()) != nProcs) {
+    if(total != nProcs || std::ssize(procSet) != nProcs) {
       amrex::AllPrint() << "**** Error in NFilesIter::FileNumbersWritten():  "
                 << " coordinatorProc nProcs total procSet.size() = "
                 << coordinatorProc << "  " << nProcs << "  "
diff --git a/Src/Base/AMReX_ParmParse.cpp b/Src/Base/AMReX_ParmParse.cpp
index b99c9348aef..8dd9d910733 100644
--- a/Src/Base/AMReX_ParmParse.cpp
+++ b/Src/Base/AMReX_ParmParse.cpp
@@ -13,6 +13,7 @@
 #include <cctype>
 #include <cstdlib>
 #include <iostream>
+#include <iterator>
 #include <limits>
 #include <numeric>
 #include <unordered_map>
@@ -903,7 +904,7 @@ void pp_entry_set_last_val (ParmParse::PP_entry const& entry, int ival, T ref, b
 #pragma omp single nowait
 #endif
     {
-        if (ival >= int(entry.m_last_vals.size())) {
+        if (ival >= std::ssize(entry.m_last_vals)) {
             entry.m_last_vals.resize(ival+1);
         }
         entry.m_last_vals[ival] = ref;
@@ -1082,7 +1083,7 @@ squeryval (const ParmParse::Table& table,
     if (!(def->empty()) && is_toml_1d_array((*def)[0])) {
         std::vector<T> toml_vals;
         read_array_1d(toml_vals, (*def)[0]);
-        if (ival >= static_cast<int>(toml_vals.size())) {
+        if (ival >= std::ssize(toml_vals)) {
             amrex::ErrorStream() << "ParmParse::queryval no value number "
                                  << ival << " for ";
             if ( occurrence ==  ParmParse::LAST ) {
@@ -1100,7 +1101,7 @@ squeryval (const ParmParse::Table& table,
     //
     // Does it have ival values?
     //
-    if ( ival >= static_cast<int>(def->size()) )
+    if (ival >= std::ssize(*def))
     {
         amrex::ErrorStream() << "ParmParse::queryval no value number"
                              << ival << " for ";
@@ -1265,7 +1266,7 @@ squeryarr (const ParmParse::Table& table,
                                            std::is_same_v<T,double>);
 
     int stop_ix = start_ix + num_val - 1;
-    if ( static_cast<int>(ref.size()) <= stop_ix )
+    if ( std::ssize(ref) <= stop_ix )
     {
         ref.resize(stop_ix + 1);
     }
@@ -2833,7 +2834,7 @@ bool squeryarrWithParser (const ParmParse::Table& table,
 
     auto const& entry = table.at(name);
 
-    AMREX_ALWAYS_ASSERT(int(vals.size()) == nvals);
+    AMREX_ALWAYS_ASSERT(std::ssize(vals) == nvals);
     for (int ival = 0; ival < nvals; ++ival) {
         bool r = pp_parser(table, parser_prefix, name, vals[ival], ptr[ival], true);
         if (r) {
diff --git a/Src/Base/AMReX_Random.cpp b/Src/Base/AMReX_Random.cpp
index 22638c1fa83..71cd002b748 100644
--- a/Src/Base/AMReX_Random.cpp
+++ b/Src/Base/AMReX_Random.cpp
@@ -5,6 +5,7 @@
 #include <AMReX_Gpu.H>
 #include <AMReX_OpenMP.H>
 
+#include <iterator>
 #include <limits>
 
 #if defined(__GNUC__) && !defined(__clang__)
@@ -206,7 +207,7 @@ UniqueRandomSubset (Vector<int> &uSet, int setSize, int poolSize,
   }
   std::set<int> copySet;
   uSet.clear();
-  while(static_cast<int>(copySet.size()) < setSize) {
+  while(std::ssize(copySet) < setSize) {
     int r = static_cast<int>(Random_int(poolSize));
     if(!copySet.contains(r)) {
       copySet.insert(r);
diff --git a/Src/Base/AMReX_TinyProfiler.cpp b/Src/Base/AMReX_TinyProfiler.cpp
index 9defd15329d..175224c44e4 100644
--- a/Src/Base/AMReX_TinyProfiler.cpp
+++ b/Src/Base/AMReX_TinyProfiler.cpp
@@ -32,8 +32,9 @@
 
 #include <algorithm>
 #include <cmath>
-#include <iostream>
 #include <iomanip>
+#include <iostream>
+#include <iterator>
 #include <set>
 
 namespace amrex {
@@ -174,7 +175,7 @@ TinyProfiler::stop ()
 
         const double t = amrex::second();
 
-        AMREX_ALWAYS_ASSERT_WITH_MESSAGE(static_cast<int>(ttstack.size()) == global_depth,
+        AMREX_ALWAYS_ASSERT_WITH_MESSAGE(std::ssize(ttstack) == global_depth,
             "TinyProfiler sections must be nested with respect to each other");
 #ifdef AMREX_USE_OMP
         AMREX_ALWAYS_ASSERT_WITH_MESSAGE(in_parallel_region == omp_in_parallel(),
diff --git a/Src/Base/AMReX_VisMF.H b/Src/Base/AMReX_VisMF.H
index b48fd1e2669..b6a3b272401 100644
--- a/Src/Base/AMReX_VisMF.H
+++ b/Src/Base/AMReX_VisMF.H
@@ -13,6 +13,7 @@
 #include <AMReX_VisMFBuffer.H>
 
 #include <fstream>
+#include <iterator>
 #include <iostream>
 #include <sstream>
 #include <deque>
@@ -405,7 +406,7 @@ Write (const FabArray<FAB>& fa, const std::string& name)
         procsWithData.insert(i);
     }
     const int nOutFiles = VisMF::GetNOutFiles();
-    if (static_cast<int>(procsWithData.size()) < nOutFiles) {
+    if (std::ssize(procsWithData) < nOutFiles) {
         useSparseFPP = true;
         for (auto i : procsWithData) {
             procsWithDataVector.push_back(i);
diff --git a/Src/Base/AMReX_VisMF.cpp b/Src/Base/AMReX_VisMF.cpp
index ea494338bd6..8951d615963 100644
--- a/Src/Base/AMReX_VisMF.cpp
+++ b/Src/Base/AMReX_VisMF.cpp
@@ -8,6 +8,7 @@
 
 #include <cerrno>
 #include <cstdio>
+#include <iterator>
 #include <limits>
 #include <vector>
 #include <utility>
@@ -1025,7 +1026,7 @@ VisMF::Write (const FabArray<FArrayBox>&    mf,
     for(int i : pmap) {
       procsWithData.insert(i);
     }
-    if(allowSparseWrites && (static_cast<int>(procsWithData.size()) < nOutFiles)) {
+    if(allowSparseWrites && (std::ssize(procsWithData) < nOutFiles)) {
       useSparseFPP = true;
 //      amrex::Print() << "SSSSSSSS:  in VisMF::Write:  useSparseFPP for:  " << mf_name << '\n';
       for (auto const& x : procsWithData) {
@@ -1823,7 +1824,7 @@ VisMF::Read (FabArray<FArrayBox> &mf,
                                                             afPtr, hdr.m_writtenRD);
                     } else {
                       auto nbytes = fab.nBytes();
-                      AMREX_ASSERT(bytesToRead > currentOffset && nbytes <= std::size_t(bytesToRead - currentOffset));
+                      AMREX_ASSERT(bytesToRead > currentOffset && std::cmp_less_equal(nbytes, (bytesToRead - currentOffset)));
                       std::memcpy(fabdata, afPtr, nbytes);
                     }
                     currentOffset += readDataItems * hdr.m_writtenRD.numBytes();
@@ -2042,7 +2043,7 @@ VisMF::Read (FabArray<FArrayBox> &mf,
       std::vector<int> recReads(nReqs, -1);
       while(nReqs > 0) {
         rmess = ParallelDescriptor::Recv(recReads, ioProcNum, readTag);
-        for(int ir(0); ir < static_cast<int>(rmess.count()); ++ir) {
+        for(std::size_t ir = 0; ir < rmess.count(); ++ir) {
           int mfIndex(recReads[ir]);
           VisMF::readFAB(mf,mfIndex, mf_name, hdr);
         }
@@ -2497,7 +2498,7 @@ VisMF::AsyncWriteDoit (const FabArray<FArrayBox>& mf, const std::string& mf_name
                 {
                     int k = -1;
                     do {
-                        if (lidx < gidx[rank].size()) {
+                        if (lidx < std::ssize(gidx[rank])) {
                             k = gidx[rank][lidx];
                             ++lidx;
                         } else {
diff --git a/Src/Base/AMReX_parmparse_fi.cpp b/Src/Base/AMReX_parmparse_fi.cpp
index 218dda63827..bd9eb02499e 100644
--- a/Src/Base/AMReX_parmparse_fi.cpp
+++ b/Src/Base/AMReX_parmparse_fi.cpp
@@ -5,6 +5,7 @@
 #include <AMReX_Print.H>
 
 #include <cstring>
+#include <iterator>
 
 using namespace amrex;
 
@@ -80,7 +81,7 @@ extern "C"
     {
         std::vector<std::string> b;
         pp->getarr(name, b);
-        BL_ASSERT(n == static_cast<int>(b.size()));
+        BL_ASSERT(n == std::ssize(b));
         for (int i = 0; i < n; ++i) {
             sv[i] = static_cast<int>(b[i].size()) + 1;
             v[i] = new char[sv[i]];
diff --git a/Src/Extern/HDF5/AMReX_ParticleHDF5.H b/Src/Extern/HDF5/AMReX_ParticleHDF5.H
index b9edfd97e96..55b8a210a94 100644
--- a/Src/Extern/HDF5/AMReX_ParticleHDF5.H
+++ b/Src/Extern/HDF5/AMReX_ParticleHDF5.H
@@ -5,6 +5,8 @@
 
 #include <AMReX_WriteBinaryParticleData.H>
 
+#include <iterator>
+
 #ifdef AMREX_USE_HDF5
 #include "hdf5.h"
 
@@ -150,8 +152,8 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     // skip the first spacedim comps for soa particles
     int first_rcomp = ParticleType::is_soa_particle ? AMREX_SPACEDIM : 0;
-    AMREX_ALWAYS_ASSERT(static_cast<int>(real_comp_names.size()) == NStructReal + NumRealComps() - first_rcomp);
-    AMREX_ALWAYS_ASSERT(static_cast<int>(int_comp_names.size()) == NStructInt  + NumIntComps() );
+    AMREX_ALWAYS_ASSERT(std::ssize(real_comp_names) == NStructReal + NumRealComps() - first_rcomp);
+    AMREX_ALWAYS_ASSERT(std::ssize(int_comp_names) == NStructInt  + NumIntComps() );
 
     Vector<int> write_real_comp;
     for (int i = first_rcomp; i < NStructReal + NumRealComps(); ++i) { write_real_comp.push_back(1); }
@@ -179,7 +181,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     // skip the first spacedim comps for soa particles
     int first_rcomp = ParticleType::is_soa_particle ? AMREX_SPACEDIM : 0;
-    AMREX_ALWAYS_ASSERT(static_cast<int>(real_comp_names.size()) == NStructReal + NumRealComps() - first_rcomp);
+    AMREX_ALWAYS_ASSERT(std::ssize(real_comp_names) == NStructReal + NumRealComps() - first_rcomp);
 
     Vector<int> write_real_comp;
     for (int i = first_rcomp; i < NStructReal + NumRealComps(); ++i) write_real_comp.push_back(1);
@@ -215,8 +217,8 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     // skip the first spacedim comps for soa particles
     int first_rcomp = ParticleType::is_soa_particle ? AMREX_SPACEDIM : 0;
-    AMREX_ALWAYS_ASSERT(static_cast<int>(write_real_comp.size()) == NStructReal + NumRealComps() - first_rcomp);
-    AMREX_ALWAYS_ASSERT(static_cast<int>(write_int_comp.size())  == NStructInt  + NumIntComps() );
+    AMREX_ALWAYS_ASSERT(std::ssize(write_real_comp) == NStructReal + NumRealComps() - first_rcomp);
+    AMREX_ALWAYS_ASSERT(std::ssize(write_int_comp)  == NStructInt  + NumIntComps() );
 
     Vector<std::string> real_comp_names;
     for (int i = first_rcomp; i < NStructReal + NumRealComps(); ++i )
@@ -305,8 +307,8 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     // skip the first spacedim comps for soa particles
     int first_rcomp = ParticleType::is_soa_particle ? AMREX_SPACEDIM : 0;
-    AMREX_ALWAYS_ASSERT(static_cast<int>(real_comp_names.size()) == NStructReal + NumRealComps() - first_rcomp);
-    AMREX_ALWAYS_ASSERT(static_cast<int>(int_comp_names.size()) == NStructInt  + NumIntComps() );
+    AMREX_ALWAYS_ASSERT(std::ssize(real_comp_names) == NStructReal + NumRealComps() - first_rcomp);
+    AMREX_ALWAYS_ASSERT(std::ssize(int_comp_names) == NStructInt  + NumIntComps() );
 
     Vector<int> write_real_comp;
     for (int i = first_rcomp; i < NStructReal + NumRealComps(); ++i) { write_real_comp.push_back(1); }
@@ -331,7 +333,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     // skip the first spacedim comps for soa particles
     int first_rcomp = ParticleType::is_soa_particle ? AMREX_SPACEDIM : 0;
-    AMREX_ALWAYS_ASSERT(static_cast<int>(real_comp_names.size()) == NStructReal + NumRealComps() - first_rcomp);
+    AMREX_ALWAYS_ASSERT(std::ssize(real_comp_names) == NStructReal + NumRealComps() - first_rcomp);
 
     Vector<int> write_real_comp;
     for (int i = first_rcomp; i < NStructReal + NumRealComps(); ++i) { write_real_comp.push_back(1); }
@@ -364,8 +366,8 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     // skip the first spacedim comps for soa particles
     int first_rcomp = ParticleType::is_soa_particle ? AMREX_SPACEDIM : 0;
-    AMREX_ALWAYS_ASSERT(static_cast<int>(write_real_comp.size()) == NStructReal + NumRealComps() - first_rcomp);
-    AMREX_ALWAYS_ASSERT(static_cast<int>(write_int_comp.size())  == NStructInt  + NumIntComps() );
+    AMREX_ALWAYS_ASSERT(std::ssize(write_real_comp) == NStructReal + NumRealComps() - first_rcomp);
+    AMREX_ALWAYS_ASSERT(std::ssize(write_int_comp)  == NStructInt  + NumIntComps() );
 
     Vector<std::string> real_comp_names;
     for (int i = first_rcomp; i < NStructReal + NumRealComps(); ++i )
@@ -448,7 +450,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     Long nparticles = 0;
     Long  maxnextid  = ParticleType::NextID();
 
-    for (int lev = 0; lev < m_particles.size();  lev++) {
+    for (int lev = 0; lev < std::ssize(m_particles);  lev++) {
         const auto& pmap = m_particles[lev];
         for (const auto& kv : pmap) {
             const auto& aos = kv.second.GetArrayOfStructs();
@@ -696,7 +698,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     // write_real_comp covers the non-position components for pure SoA)
     int real_comp_count = AMREX_SPACEDIM; // position values
 
-    for (int i = 0; i < static_cast<int>(write_real_comp.size()); ++i ) {
+    for (int i = 0; i < std::ssize(write_real_comp); ++i ) {
         if (write_real_comp[i]) { ++real_comp_count; }
     }
 
@@ -1354,7 +1356,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
             }
         }
 
-        for(int igrid = 0; igrid < static_cast<int>(grids_to_read.size()); ++igrid) {
+        for(int igrid = 0; igrid < std::ssize(grids_to_read); ++igrid) {
             const int grid = grids_to_read[igrid];
 
             if (how == "single") {
@@ -1402,7 +1404,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     BL_PROFILE("ParticleContainer::ReadParticlesHDF5()");
     AMREX_ASSERT(cnt > 0);
-    AMREX_ASSERT(lev < int(m_particles.size()));
+    AMREX_ASSERT(lev < std::ssize(m_particles));
 
     hid_t int_dspace, int_fspace, real_dspace, real_fspace;
 
@@ -1552,7 +1554,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
         }
     }
 
-    for (int host_lev = 0; host_lev < static_cast<int>(host_particles.size()); ++host_lev)
+    for (int host_lev = 0; host_lev < std::ssize(host_particles); ++host_lev)
     {
         for (auto& kv : host_particles[host_lev]) {
             auto grid = kv.first.first;
diff --git a/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H b/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H
index eee085f812f..0dde1dd23bc 100644
--- a/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H
+++ b/Src/Extern/HDF5/AMReX_WriteBinaryParticleDataHDF5.H
@@ -1,6 +1,8 @@
 #ifndef AMREX_WRITE_BINARY_PARTICLE_DATA_HDF5_H
 #define AMREX_WRITE_BINARY_PARTICLE_DATA_HDF5_H
 
+#include <iterator>
+
 /**
  * \file AMReX_WriteBinaryParticleDataHDF5.H
  *
@@ -203,7 +205,7 @@ void WriteHDF5ParticleDataSync (PC const& pc,
     {
         int nrc = PC::ParticleType::is_soa_particle ?
             pc.NumRealComps() + NStructReal - AMREX_SPACEDIM : pc.NumRealComps() + NStructReal;
-        AMREX_ALWAYS_ASSERT(static_cast<int>(real_comp_names.size()) == nrc);
+        AMREX_ALWAYS_ASSERT(std::ssize(real_comp_names) == nrc);
     }
     AMREX_ALWAYS_ASSERT( int_comp_names.size() == pc.NumIntComps() + NStructInt);
 
@@ -262,7 +264,7 @@ void WriteHDF5ParticleDataSync (PC const& pc,
     // evaluate f for every particle to determine which ones to output
     Vector<std::map<std::pair<int, int>, typename PC::IntVector > >
         particle_io_flags(pc.GetParticles().size());
-    for (int lev = 0; lev < pc.GetParticles().size();  lev++)
+    for (int lev = 0; lev < std::ssize(pc.GetParticles());  lev++)
     {
         const auto& pmap = pc.GetParticles(lev);
         for (const auto& kv : pmap)
@@ -339,7 +341,7 @@ void WriteHDF5ParticleDataSync (PC const& pc,
         CreateWriteHDF5AttrString(fid, "version_name", versionName.c_str());
 
         int num_output_real = 0;
-        for (int i = 0; i < static_cast<int>(write_real_comp.size()); ++i) {
+        for (int i = 0; i < std::ssize(write_real_comp); ++i) {
             if (write_real_comp[i]) { ++num_output_real; }
         }
 
@@ -364,7 +366,7 @@ void WriteHDF5ParticleDataSync (PC const& pc,
         // Real component names
         int real_comp_count = AMREX_SPACEDIM; // position values
 
-        for (int i = 0; i < static_cast<int>(write_real_comp.size()); ++i ) {
+        for (int i = 0; i < std::ssize(write_real_comp); ++i ) {
             if (write_real_comp[i]) {
                 /* HdrFile << real_comp_names[i] << '\n'; */
                 snprintf(comp_name, sizeof comp_name, "real_component_%d", real_comp_count);
diff --git a/Src/LinearSolvers/MLMG/AMReX_MLLinOp.H b/Src/LinearSolvers/MLMG/AMReX_MLLinOp.H
index e51c05cefba..3a0804b48c1 100644
--- a/Src/LinearSolvers/MLMG/AMReX_MLLinOp.H
+++ b/Src/LinearSolvers/MLMG/AMReX_MLLinOp.H
@@ -24,6 +24,7 @@
 #include <AMReX_MultiFabUtil.H>
 
 #include <algorithm>
+#include <iterator>
 #include <string>
 
 namespace amrex {
@@ -837,7 +838,7 @@ MLLinOpT<MF>::defineGrids (const Vector<Geometry>& a_geom,
 #endif
 
     m_num_amr_levels = 0;
-    for (int amrlev = 0; amrlev < a_geom.size(); amrlev++) {
+    for (int amrlev = 0; amrlev < std::ssize(a_geom); amrlev++) {
         if (!a_grids[amrlev].empty()) {
             m_num_amr_levels++;
         }
@@ -875,7 +876,7 @@ MLLinOpT<MF>::defineGrids (const Vector<Geometry>& a_geom,
         m_geom[amrlev].push_back(a_geom[amrlev]);
         m_grids[amrlev].push_back(a_grids[amrlev]);
         m_dmap[amrlev].push_back(a_dmap[amrlev]);
-        if (amrlev < a_factory.size()) {
+        if (amrlev < std::ssize(a_factory)) {
             m_factory[amrlev].emplace_back(a_factory[amrlev]->clone());
         } else {
             m_factory[amrlev].push_back(std::make_unique<DefaultFabFactory<FAB>>());
@@ -1332,7 +1333,7 @@ MLLinOpT<MF>::makeAgglomeratedDMap (const Vector<BoxArray>& ba,
             const std::vector< std::vector<int> >& sfc = DistributionMapping::makeSFC(ba[i]);
 
             const int nprocs = ParallelContext::NProcsSub();
-            AMREX_ASSERT(static_cast<int>(sfc.size()) == nprocs);
+            AMREX_ASSERT(std::ssize(sfc) == nprocs);
 
             Vector<int> pmap(ba[i].size());
             for (int iproc = 0; iproc < nprocs; ++iproc) {
diff --git a/Src/Particle/AMReX_NeighborParticlesI.H b/Src/Particle/AMReX_NeighborParticlesI.H
index 3a9f1a670ae..e07329c4f93 100644
--- a/Src/Particle/AMReX_NeighborParticlesI.H
+++ b/Src/Particle/AMReX_NeighborParticlesI.H
@@ -1,4 +1,6 @@
 
+#include <iterator>
+
 namespace amrex {
 
 template <int NStructReal, int NStructInt, int NArrayReal, int NArrayInt>
@@ -339,7 +341,7 @@ NeighborParticleContainer<NStructReal, NStructInt, NArrayReal, NArrayInt>
 
     for (int lev = 0; lev < this->numLevels(); ++lev) {
         // resize our temporaries in serial
-        for (int i = 0; i < static_cast<int>(local_neighbors.size()); ++i) {
+        for (int i = 0; i < std::ssize(local_neighbors); ++i) {
             const NeighborCommTag& comm_tag = local_neighbors[i];
             tmp_remote_map[comm_tag].resize(num_threads);
             remote_map[comm_tag];
@@ -376,7 +378,7 @@ NeighborParticleContainer<NStructReal, NStructInt, NArrayReal, NArrayInt>
                     getNeighborTags(tags, p, m_num_neighbor_cells, src_tag, pti);
 
                     // Add neighbors to buffers
-                    for (int j = 0; j < static_cast<int>(tags.size()); ++j) {
+                    for (int j = 0; j < std::ssize(tags); ++j) {
                         NeighborCopyTag& tag = tags[j];
                         PairIndex dst_index(tag.grid, tag.tile);
                         if (tag.grid < 0) { continue; }
@@ -1112,7 +1114,7 @@ resizeContainers (int num_levels)
 {
     this->reserveData();
     this->resizeData();
-    if ( static_cast<int>(neighbors.size()) <= num_levels )
+    if ( std::ssize(neighbors) <= num_levels )
     {
         neighbors.resize(num_levels);
         m_neighbor_list.resize(num_levels);
diff --git a/Src/Particle/AMReX_ParticleCommunication.H b/Src/Particle/AMReX_ParticleCommunication.H
index 58496e389e6..3c21daf9f79 100644
--- a/Src/Particle/AMReX_ParticleCommunication.H
+++ b/Src/Particle/AMReX_ParticleCommunication.H
@@ -14,6 +14,7 @@
 #include <AMReX_ParmParse.H>
 
 #include <algorithm>
+#include <iterator>
 #include <map>
 #include <numeric>
 #include <utility>
@@ -27,7 +28,7 @@ struct NeighborUnpackPolicy
     template <class PTile>
     void resizeTiles (std::vector<PTile*>& tiles, const std::vector<int>& sizes, std::vector<int>& offsets) const
     {
-        for(int i = 0; i < static_cast<int>(sizes.size()); ++i)
+        for(int i = 0; i < std::ssize(sizes); ++i)
         {
             int offset = tiles[i]->numTotalParticles();
             int nn = tiles[i]->getNumNeighbors();
@@ -485,12 +486,12 @@ public:
         if constexpr (!PC::ParticleType::is_soa_particle) {
             comm_comps_start += AMREX_SPACEDIM + NStructReal;
         }
-        for (int i = comm_comps_start; i < real_comp_mask.size(); ++i) {
+        for (int i = comm_comps_start; i < std::ssize(real_comp_mask); ++i) {
             if (real_comp_mask[i]) {++num_real_comm_comp;}
         }
 
         int num_int_comm_comp = 0;
-        for (int i = 2 + NStructInt; i < int_comp_mask.size(); ++i) {
+        for (int i = 2 + NStructInt; i < std::ssize(int_comp_mask); ++i) {
             if (int_comp_mask[i])  {++num_int_comm_comp;}
         }
 
@@ -1025,7 +1026,7 @@ void unpackRemotes (PC& pc, const ParticleCopyPlan& plan, Buffer& rcv_buffer, Un
 
         std::vector<int> sizes;
         std::vector<PTile*> tiles;
-        for (int i = 0, N = int(plan.m_rcv_box_counts.size()); i < N; ++i)
+        for (int i = 0; i < std::ssize(plan.m_rcv_box_counts); ++i)
         {
             int copy_size = plan.m_rcv_box_counts[i];
             int lev = plan.m_rcv_box_levs[i];
@@ -1041,7 +1042,7 @@ void unpackRemotes (PC& pc, const ParticleCopyPlan& plan, Buffer& rcv_buffer, Un
         Gpu::streamSynchronize();
         int uindex = 0;
         int procindex = 0, rproc = plan.m_rcv_box_pids[0];
-        for (int i = 0, N = int(plan.m_rcv_box_counts.size()); i < N; ++i)
+        for (int i = 0; i < std::ssize(plan.m_rcv_box_counts); ++i)
         {
             int lev = plan.m_rcv_box_levs[i];
             int gid = plan.m_rcv_box_ids[i];
diff --git a/Src/Particle/AMReX_ParticleCommunication.cpp b/Src/Particle/AMReX_ParticleCommunication.cpp
index 898c3f78612..092178d47ac 100644
--- a/Src/Particle/AMReX_ParticleCommunication.cpp
+++ b/Src/Particle/AMReX_ParticleCommunication.cpp
@@ -2,6 +2,8 @@
 #include <AMReX_ParticleContainerBase.H>
 #include <AMReX_ParallelDescriptor.H>
 
+#include <iterator>
+
 namespace amrex {
 
 void ParticleCopyOp::clear ()
@@ -24,7 +26,7 @@ void ParticleCopyOp::setNumLevels (int num_levels)
 
 void ParticleCopyOp::resize (int gid, int tid, int lev, int size)
 {
-    if (lev >= m_boxes.size())
+    if (lev >= std::ssize(m_boxes))
     {
         setNumLevels(lev+1);
     }
@@ -406,8 +408,8 @@ void ParticleCopyPlan::doHandShakeOneSided (const ParticleContainerBase& pc,
     const int MyProc = ParallelContext::MyProcSub();
     const int NProcs = ParallelContext::NProcsSub();
 
-    AMREX_ALWAYS_ASSERT(static_cast<int>(Snds.size()) == NProcs);
-    AMREX_ALWAYS_ASSERT(static_cast<int>(Rcvs.size()) == NProcs);
+    AMREX_ALWAYS_ASSERT(std::ssize(Snds) == NProcs);
+    AMREX_ALWAYS_ASSERT(std::ssize(Rcvs) == NProcs);
 
     pc.ensureParticleHandshakeWindow();
     auto* handshake_buffer = pc.particleHandshakeBuffer();
diff --git a/Src/Particle/AMReX_ParticleContainerI.H b/Src/Particle/AMReX_ParticleContainerI.H
index e0eb6c8496c..67646afba61 100644
--- a/Src/Particle/AMReX_ParticleContainerI.H
+++ b/Src/Particle/AMReX_ParticleContainerI.H
@@ -6,6 +6,7 @@
 #include <stdexcept>
 #include <string>
 #include <type_traits>
+#include <utility>
 #include <vector>
 
 namespace amrex {
@@ -110,8 +111,8 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     std::vector<std::string> const & rdata_name, std::vector<std::string> const & idata_name
 )
 {
-    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(rdata_name.size() == NArrayReal, "rdata_name must be equal to NArrayReal");
-    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(idata_name.size() == NArrayInt, "idata_name must be equal to NArrayInt");
+    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(std::ssize(rdata_name) == NArrayReal, "rdata_name must be equal to NArrayReal");
+    AMREX_ALWAYS_ASSERT_WITH_MESSAGE(std::ssize(idata_name) == NArrayInt, "idata_name must be equal to NArrayInt");
 
     // ensure names for components are unique
     std::set<std::string> const unique_r_names(rdata_name.begin(), rdata_name.end());
@@ -256,7 +257,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
           bool findfirst = (nGrow == 0) ? true : false;
           ba.intersections(Box(iv, iv), isects, findfirst, nGrow);
           grid = isects.empty() ? -1 : isects[0].first;
-          if (nGrow > 0 && isects.size() > 1) {
+          if (nGrow > 0 && std::ssize(isects) > 1) {
              for (auto & isect : isects) {
                  Box bx = ba.getCellCenteredBox(isect.first);
                  for (int dir = 0; dir < AMREX_SPACEDIM; ++dir) {
@@ -495,7 +496,7 @@ template <typename ParticleType, int NArrayReal, int NArrayInt,
 Vector<Long>
 ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssignor>::NumberOfParticlesInGrid (int lev, bool only_valid, bool only_local) const
 {
-    AMREX_ASSERT(lev >= 0 && lev < int(m_particles.size()));
+    AMREX_ASSERT(lev >= 0 && lev < std::ssize(m_particles));
 
     LayoutData<Long> np_per_grid_local(ParticleBoxArray(lev),
                                        ParticleDistributionMap(lev));
@@ -552,7 +553,7 @@ Long ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, Cell
 {
     Long nparticles = 0;
 
-    if (level < 0 || level >= int(m_particles.size())) { return nparticles; }
+    if (level < 0 || level >= std::ssize(m_particles)) { return nparticles; }
 
     if (only_valid) {
         ReduceOps<ReduceOpSum> reduce_op;
@@ -592,7 +593,7 @@ template <typename I, std::enable_if_t<std::is_integral_v<I> && (sizeof(I) >= si
 void
 ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssignor>::CapacityOfParticlesInGrid (LayoutData<I>& mem, int lev) const
 {
-    AMREX_ASSERT(lev >= 0 && lev < int(m_particles.size()));
+    AMREX_ASSERT(lev >= 0 && lev < std::ssize(m_particles));
 
     AMREX_ASSERT(BoxArray::SameRefs(mem.boxArray(), ParticleBoxArray(lev)) &&
                  mem.DistributionMap() == ParticleDistributionMap(lev));
@@ -723,7 +724,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 
     AMREX_ASSERT(OK());
     if (m_particles.empty()) { return; }
-    AMREX_ASSERT(lev >= 0 && lev < int(m_particles.size()));
+    AMREX_ASSERT(lev >= 0 && lev < std::ssize(m_particles));
     AMREX_ASSERT(numParticlesOutOfRange(*this, 0) == 0);
 
     const auto& geom = Geom(lev);
@@ -757,7 +758,7 @@ void
 ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssignor>::RemoveParticlesAtLevel (int level)
 {
     BL_PROFILE("ParticleContainer::RemoveParticlesAtLevel()");
-    if (level >= int(this->m_particles.size())) { return; }
+    if (level >= std::ssize(this->m_particles)) { return; }
 
     if (!this->m_particles[level].empty())
     {
@@ -771,7 +772,7 @@ void
 ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssignor>::RemoveParticlesNotAtFinestLevel ()
 {
   BL_PROFILE("ParticleContainer::RemoveParticlesNotAtFinestLevel()");
-  AMREX_ASSERT(this->finestLevel()+1 == int(this->m_particles.size()));
+  AMREX_ASSERT(this->finestLevel()+1 == std::ssize(this->m_particles));
 
   Long cnt = 0;
 
@@ -852,7 +853,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     AMREX_ASSERT(level > 0);
     AMREX_ASSERT(virts.empty());
 
-    if (level >= static_cast<int>(m_particles.size())) {
+    if (level >= std::ssize(m_particles)) {
         return;
     }
 
@@ -1097,7 +1098,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     AMREX_ASSERT(ghosts.empty());
     AMREX_ASSERT(level < finestLevel());
 
-    if (level >= static_cast<int>(m_particles.size())) {
+    if (level >= std::ssize(m_particles)) {
         return;
     }
 
@@ -1129,7 +1130,7 @@ clearParticles ()
 {
     BL_PROFILE("ParticleContainer::clearParticles()");
 
-    for (int lev = 0; lev < static_cast<int>(m_particles.size()); ++lev)
+    for (int lev = 0; lev < std::ssize(m_particles); ++lev)
     {
         for (auto& kv : m_particles[lev]) { kv.second.resize(0); }
         particle_detail::clearEmptyEntries(m_particles[lev]);
@@ -1447,7 +1448,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     int theEffectiveFinestLevel = m_gdb->finestLevel();
     while (!m_gdb->LevelDefined(theEffectiveFinestLevel)) { theEffectiveFinestLevel--; }
 
-    if (int(m_particles.size()) < theEffectiveFinestLevel+1) {
+    if (std::ssize(m_particles) < theEffectiveFinestLevel+1) {
         if (Verbose()) {
             amrex::Print() << "ParticleContainer::Redistribute() resizing containers from "
                            << m_particles.size() << " to "
@@ -1690,12 +1691,12 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
         particle_detail::clearEmptyEntries(m_particles[lev]);
     }
 
-    if (int(m_particles.size()) > theEffectiveFinestLevel+1) {
+    if (std::ssize(m_particles) > theEffectiveFinestLevel+1) {
         if (m_verbose > 0) {
             amrex::Print() << "ParticleContainer::Redistribute() resizing m_particles from "
                         << m_particles.size() << " to " << theEffectiveFinestLevel+1 << '\n';
         }
-        AMREX_ASSERT(int(m_particles.size()) >= 2);
+        AMREX_ASSERT(std::ssize(m_particles) >= 2);
 
         m_particles.resize(theEffectiveFinestLevel + 1);
         m_dummy_mf.resize(theEffectiveFinestLevel + 1);
@@ -1764,7 +1765,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     }
 
     if (plan.m_nrcvs > 0) {
-        for (int i = 0, N = int(plan.m_rcv_box_counts.size()); i < N; ++i) {
+        for (int i = 0; i < std::ssize(plan.m_rcv_box_counts); ++i) {
             int copy_size = plan.m_rcv_box_counts[i];
             int lev = plan.m_rcv_box_levs[i];
             int gid = plan.m_rcv_box_ids[i];
@@ -1810,7 +1811,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     BL_PROFILE("ParticleContainer::AddParticlesAtLevel()");
 
-    if (int(m_particles.size()) < level+1)
+    if (std::ssize(m_particles) < level+1)
     {
         if (Verbose())
         {
diff --git a/Src/Particle/AMReX_ParticleIO.H b/Src/Particle/AMReX_ParticleIO.H
index 8a35ad4e138..b6ce9058910 100644
--- a/Src/Particle/AMReX_ParticleIO.H
+++ b/Src/Particle/AMReX_ParticleIO.H
@@ -5,6 +5,8 @@
 #include <AMReX_WriteBinaryParticleData.H>
 #include <AMReX_VisMF.H>
 
+#include <iterator>
+
 namespace amrex {
 
 template <typename ParticleType, int NArrayReal, int NArrayInt,
@@ -456,7 +458,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     Long nparticles = 0;
     Long  maxnextid  = ParticleType::NextID();
 
-    for (int lev = 0; lev < m_particles.size();  lev++) {
+    for (int lev = 0; lev < std::ssize(m_particles);  lev++) {
         const auto& pmap = m_particles[lev];
         for (const auto& kv : pmap) {
             const auto& aos = kv.second.GetArrayOfStructs();
@@ -534,7 +536,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
                     cnt[whichPrePost[lev][i]] += countPrePost[lev][i];
                 }
 
-                for(int i(0), N = int(cnt.size()); i < N; ++i) {
+                for(int i = 0; i < std::ssize(cnt); ++i) {
                     if(cnt[i] == 0) {
                         std::string FullFileName = NFilesIter::FileName(i, filePrefixPrePost[lev]);
                         FileSystem::Remove(FullFileName);
@@ -957,7 +959,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 {
     BL_PROFILE("ParticleContainer::ReadParticles()");
     AMREX_ASSERT(cnt > 0);
-    AMREX_ASSERT(lev < int(m_particles.size()));
+    AMREX_ASSERT(lev < std::ssize(m_particles));
 
     // First read in the integer data in binary.  We do not store
     // the m_lev and m_grid data on disk.  We can easily recreate
@@ -1080,7 +1082,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
         }
     }
 
-    for (int host_lev = 0; host_lev < static_cast<int>(host_particles.size()); ++host_lev)
+    for (int host_lev = 0; host_lev < std::ssize(host_particles); ++host_lev)
     {
         for (auto& kv : host_particles[host_lev]) {
             auto grid = kv.first.first;
@@ -1144,7 +1146,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
     //
     Long nparticles = 0;
 
-    for (int lev = 0; lev < m_particles.size();  lev++) {
+    for (int lev = 0; lev < std::ssize(m_particles);  lev++) {
         auto& pmap = m_particles[lev];
         for (const auto& kv : pmap) {
             const auto& aos = kv.second.GetArrayOfStructs();
@@ -1221,7 +1223,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
                 amrex::FileOpenFailed(filename);
             }
 
-            for (int lev = 0; lev < m_particles.size();  lev++) {
+            for (int lev = 0; lev < std::ssize(m_particles);  lev++) {
                 auto& pmap = m_particles[lev];
                 for (const auto& kv : pmap) {
                     ParticleTile<ParticleType, NArrayReal, NArrayInt,
diff --git a/Src/Particle/AMReX_ParticleInit.H b/Src/Particle/AMReX_ParticleInit.H
index ae27d70e884..5b45e4ae17c 100644
--- a/Src/Particle/AMReX_ParticleInit.H
+++ b/Src/Particle/AMReX_ParticleInit.H
@@ -2,6 +2,9 @@
 #define AMREX_PARTICLEINIT_H
 #include <AMReX_Config.H>
 
+#include <iterator>
+#include <utility>
+
 namespace amrex {
 
 /*
@@ -321,7 +324,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
             }
         }
 
-        for (int lev = 0; lev < static_cast<int>(host_particles.size()); ++lev)
+        for (int lev = 0; lev < std::ssize(host_particles); ++lev)
         {
             for (auto& kv : host_particles[lev])
             {
@@ -338,7 +341,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
                 Gpu::copyAsync(Gpu::hostToDevice, src_tile.begin(), src_tile.end(),
                                dst_tile.GetArrayOfStructs().begin() + old_size);
 
-                if((host_real_attribs[lev][std::make_pair(grid, tile)]).size() > (long unsigned int) NArrayReal) {
+                if (std::ssize(host_real_attribs[lev][std::make_pair(grid, tile)]) > NArrayReal) {
                     for (int i = 0; i < NArrayReal; ++i) {
                         Gpu::copyAsync(Gpu::hostToDevice,
                                        host_real_attribs[lev][std::make_pair(grid,tile)][i].begin(),
@@ -379,7 +382,8 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
                 Where(p, pld);
 
                 host_particles[pld.m_lev][std::make_pair(pld.m_grid, pld.m_tile)].push_back(p);
-                if((host_real_attribs[pld.m_lev][std::make_pair(pld.m_grid, pld.m_tile)]).size() > (long unsigned int) (extradata - NStructReal)) {
+                if (std::ssize(host_real_attribs[pld.m_lev][std::make_pair(pld.m_grid, pld.m_tile)]) >
+                    extradata - NStructReal) {
                     for (int n = NStructReal; n < extradata; n++)
                     {
                         Real rdata = nreals[n-NStructReal].back();
@@ -398,7 +402,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
             }
         }
 
-        for (int lev = 0; lev < static_cast<int>(host_particles.size()); ++lev)
+        for (int lev = 0; lev < std::ssize(host_particles); ++lev)
         {
             for (auto& kv : host_particles[lev])
             {
@@ -574,9 +578,9 @@ InitFromBinaryFile (const std::string& file,
 
                 readers.insert(n);
             }
-            while (static_cast<int>(readers.size()) < NReaders);
+            while (std::ssize(readers) < NReaders);
 
-            AMREX_ASSERT(static_cast<Long>(readers.size()) == rprocs.size());
+            AMREX_ASSERT(std::ssize(readers) == rprocs.size());
 
             int i = 0;
 
@@ -598,7 +602,7 @@ InitFromBinaryFile (const std::string& file,
         //
         readers.insert(rprocs.begin(), rprocs.end());
 
-        AMREX_ASSERT(static_cast<Long>(readers.size()) == rprocs.size());
+        AMREX_ASSERT(std::ssize(readers) == rprocs.size());
 
         AMREX_ASSERT(rprocs.size() == NReaders);
     }
@@ -845,7 +849,7 @@ InitFromBinaryFile (const std::string& file,
             how_many_read += NRead;
         }
 
-        for (int host_lev = 0; host_lev < static_cast<int>(host_particles.size()); ++host_lev)
+        for (int host_lev = 0; host_lev < std::ssize(host_particles); ++host_lev)
         {
             for (auto& kv : host_particles[host_lev]) {
                 auto grid = kv.first.first;
@@ -870,7 +874,7 @@ InitFromBinaryFile (const std::string& file,
         // we don't keep trying to redistribute particles that have
         // already been redistributed correctly.
         //
-        for (int lev = 0; lev < m_particles.size(); lev++)
+        for (int lev = 0; lev < std::ssize(m_particles); lev++)
         {
             auto& pmap     = m_particles[lev];
             auto& tmp_pmap = tmp_particles[lev];
@@ -1142,7 +1146,7 @@ InitRandom (Long                    icount,
             }
         }
 
-        for (int host_lev = 0; host_lev < static_cast<int>(host_particles.size()); ++host_lev)
+        for (int host_lev = 0; host_lev < std::ssize(host_particles); ++host_lev)
         {
             for (auto& kv : host_particles[host_lev]) {
                 auto grid = kv.first.first;
@@ -1295,7 +1299,7 @@ InitRandom (Long                    icount,
             }
         }
 
-        for (int host_lev = 0; host_lev < static_cast<int>(host_particles.size()); ++host_lev)
+        for (int host_lev = 0; host_lev < std::ssize(host_particles); ++host_lev)
         {
             for (auto& kv : host_particles[host_lev]) {
                 auto grid = kv.first.first;
@@ -1387,7 +1391,7 @@ ParticleContainer_impl<ParticleType, NArrayReal, NArrayInt, Allocator, CellAssig
 
     m_particles.resize(m_gdb->finestLevel()+1);
 
-    for (int lev = 0; lev < m_particles.size(); lev++)
+    for (int lev = 0; lev < std::ssize(m_particles); lev++)
     {
         AMREX_ASSERT(m_particles[lev].empty());
     }
@@ -1561,7 +1565,7 @@ InitNRandomPerCell (int n_per_cell, const ParticleInitData& pdata)
 
     resizeData();
 
-    for (int lev = 0; lev < m_particles.size(); lev++) {
+    for (int lev = 0; lev < std::ssize(m_particles); lev++) {
         AMREX_ASSERT(m_particles[lev].empty());
     }
 
@@ -1639,7 +1643,7 @@ InitNRandomPerCell (int n_per_cell, const ParticleInitData& pdata)
             }
         }
 
-        for (int host_lev = 0; host_lev < static_cast<int>(host_particles.size()); ++host_lev)
+        for (int host_lev = 0; host_lev < std::ssize(host_particles); ++host_lev)
         {
             for (auto& kv : host_particles[host_lev]) {
                 auto gid = kv.first.first;
diff --git a/Src/Particle/AMReX_ParticleReduce.H b/Src/Particle/AMReX_ParticleReduce.H
index c8bacdf0b55..91ca686589f 100644
--- a/Src/Particle/AMReX_ParticleReduce.H
+++ b/Src/Particle/AMReX_ParticleReduce.H
@@ -11,6 +11,7 @@
 #include <AMReX_ParticleUtil.H>
 #include <AMReX_Vector.H>
 
+#include <iterator>
 #include <limits>
 #include <type_traits>
 
@@ -234,7 +235,7 @@ ReduceSum (PC const& pc, int lev_min, int lev_max, F const& f)
 #ifdef AMREX_USE_OMP
 #pragma omp parallel for if (!system::regtest_reduction) reduction(+:sm)
 #endif
-            for (int pmap_it = 0; pmap_it < static_cast<int>(ptile_ptrs.size()); ++pmap_it)
+            for (int pmap_it = 0; pmap_it < std::ssize(ptile_ptrs); ++pmap_it)
             {
                 const auto& tile = plev.at(grid_tile_ids[pmap_it]);
                 const auto np = tile.numParticles();
@@ -438,7 +439,7 @@ ReduceMax (PC const& pc, int lev_min, int lev_max, F const& f)
 #ifdef AMREX_USE_OMP
 #pragma omp parallel for if (!system::regtest_reduction) reduction(max:r)
 #endif
-            for (int pmap_it = 0; pmap_it < static_cast<int>(ptile_ptrs.size()); ++pmap_it)
+            for (int pmap_it = 0; pmap_it < std::ssize(ptile_ptrs); ++pmap_it)
             {
                 const auto& tile = plev.at(grid_tile_ids[pmap_it]);
                 const auto np = tile.numParticles();
@@ -641,7 +642,7 @@ ReduceMin (PC const& pc, int lev_min, int lev_max, F const& f)
 #ifdef AMREX_USE_OMP
 #pragma omp parallel for if (!system::regtest_reduction) reduction(min:r)
 #endif
-            for (int pmap_it = 0; pmap_it < static_cast<int>(ptile_ptrs.size()); ++pmap_it)
+            for (int pmap_it = 0; pmap_it < std::ssize(ptile_ptrs); ++pmap_it)
             {
                 const auto& tile = plev.at(grid_tile_ids[pmap_it]);
                 const auto np = tile.numParticles();
@@ -839,7 +840,7 @@ ReduceLogicalAnd (PC const& pc, int lev_min, int lev_max, F const& f)
 #ifdef AMREX_USE_OMP
 #pragma omp parallel for if (!system::regtest_reduction) reduction(&&:r)
 #endif
-            for (int pmap_it = 0; pmap_it < static_cast<int>(ptile_ptrs.size()); ++pmap_it)
+            for (int pmap_it = 0; pmap_it < std::ssize(ptile_ptrs); ++pmap_it)
             {
                 const auto& tile = plev.at(grid_tile_ids[pmap_it]);
                 const auto np = tile.numParticles();
@@ -1038,7 +1039,7 @@ ReduceLogicalOr (PC const& pc, int lev_min, int lev_max, F const& f)
 #ifdef AMREX_USE_OMP
 #pragma omp parallel for if (!system::regtest_reduction) reduction(||:r)
 #endif
-            for (int pmap_it = 0; pmap_it < static_cast<int>(ptile_ptrs.size()); ++pmap_it)
+            for (int pmap_it = 0; pmap_it < std::ssize(ptile_ptrs); ++pmap_it)
             {
                 const auto& tile = plev.at(grid_tile_ids[pmap_it]);
                 const auto np = tile.numParticles();
@@ -1278,7 +1279,7 @@ ParticleReduce (PC const& pc, int lev_min, int lev_max, F const& f, ReduceOps& r
 #if !defined(AMREX_USE_GPU) && defined(AMREX_USE_OMP)
 #pragma omp parallel for
 #endif
-        for (int pmap_it = 0; pmap_it < static_cast<int>(ptile_ptrs.size()); ++pmap_it)
+        for (int pmap_it = 0; pmap_it < std::ssize(ptile_ptrs); ++pmap_it)
         {
             const auto& tile = plev.at(grid_tile_ids[pmap_it]);
             const auto np = tile.numParticles();
diff --git a/Tests/ParmParse/main.cpp b/Tests/ParmParse/main.cpp
index 8bd54e37c44..3f7b7db4be6 100644
--- a/Tests/ParmParse/main.cpp
+++ b/Tests/ParmParse/main.cpp
@@ -320,7 +320,7 @@ int main(int argc, char* argv[])
 
         std::vector<std::string> sv{"string a", " string b", " string c ", "string-d"};
         pp.addarr("string_vector", sv);
-        for (int i = 0; i < int(sv.size()); ++i) {
+        for (int i = 0; i < std::ssize(sv); ++i) {
             pp.get("string_vector", s, i);
             AMREX_ALWAYS_ASSERT(s == sv[i]);
         }