diff --git a/Cargo.toml b/Cargo.toml
index 9fc5fb0..384860d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,7 +12,13 @@ description = "Formats whitespace in a SQL string to make it easier to read"
 keywords = ["sql"]
 categories = ["development-tools"]
 
+[features]
+debug = ["dep:anstream", "dep:anstyle", "dep:okhsl"]
+
 [dependencies]
+anstream = { version = "0.6.21", optional = true }
+anstyle = { version  = "1.0.13", optional = true }
+okhsl = { version = "1.0.1", optional = true }
 unicode_categories = "0.1.1"
 winnow = { version = "0.7.0", features = ["simd"] }
 
diff --git a/src/debug.rs b/src/debug.rs
new file mode 100644
index 0000000..aaadea7
--- /dev/null
+++ b/src/debug.rs
@@ -0,0 +1,25 @@
+use std::hash::{DefaultHasher, Hash, Hasher};
+
+use anstyle::RgbColor;
+
+pub(crate) trait ToColor {
+    fn to_color(&self) -> RgbColor;
+}
+
+impl<T: Hash> ToColor for T {
+    fn to_color(&self) -> RgbColor {
+        let mut s = DefaultHasher::new();
+        self.hash(&mut s);
+
+        let v = s.finish();
+
+        let v = ((v >> 32) as u32) ^ (v as u32);
+
+        let h = v as f64 / u32::MAX as f64;
+
+        let c = okhsl::Okhsv { h, s: 0.7, v: 0.9 };
+        let r = c.to_srgb();
+
+        RgbColor(r.r, r.g, r.b)
+    }
+}
diff --git a/src/formatter.rs b/src/formatter.rs
index 58d37c8..12f00a0 100644
--- a/src/formatter.rs
+++ b/src/formatter.rs
@@ -139,6 +139,43 @@ pub(crate) fn format(
                 }
             },
         }
+
+        #[cfg(feature = "debug")]
+        {
+            use crate::debug::*;
+            let b = anstyle::Style::new().bold();
+            let k = b.fg_color(Some(token.kind.to_color().into()));
+            let rk = k.render_reset();
+            let k = k.render();
+            let d = anstyle::Style::new().dimmed();
+            let rd = d.render_reset();
+            let d = d.render();
+
+            let kind = format!("{:?}", token.kind);
+
+            let mut lines = formatted_query
+                .lines()
+                .rev()
+                .filter(|l| !l.trim().is_empty());
+            let line = lines.next().unwrap_or(formatted_query.as_str());
+            let value = match token.kind {
+                TokenKind::Whitespace => {
+                    let s = token
+                        .value
+                        .chars()
+                        .map(|c| match c {
+                            '\n' => Cow::Borrowed(r"\n"),
+                            '\t' => Cow::Borrowed(r"\t"),
+                            '\r' => Cow::Borrowed(r"\r"),
+                            _ => c.to_string().into(),
+                        })
+                        .collect::<String>();
+                    s.into()
+                }
+                _ => Cow::Borrowed(token.value),
+            };
+            anstream::eprintln!("{k}{:21}{rk}: {d}{:50}{rd} {line}", kind, value);
+        }
     }
     formatted_query.trim().to_string()
 }
diff --git a/src/lib.rs b/src/lib.rs
index 2f7b28f..9734e70 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -15,6 +15,9 @@ mod inline_block;
 mod params;
 mod tokenizer;
 
+#[cfg(feature = "debug")]
+mod debug;
+
 /// Formats whitespace in a SQL string to make it easier to read.
 /// Optionally replaces parameter placeholders with `params`.
 pub fn format(query: &str, params: &QueryParams, options: &FormatOptions) -> String {
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index ab813f6..de125dc 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -73,7 +73,7 @@ pub(crate) struct Token<'a> {
     pub alias: &'a str,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub(crate) enum TokenKind {
     TypeSpecifier,
     Whitespace,