diff --git a/src/browser/dom/document.zig b/src/browser/dom/document.zig
index a82ec6e35..d3e71ff30 100644
--- a/src/browser/dom/document.zig
+++ b/src/browser/dom/document.zig
@@ -36,6 +36,8 @@ const CSSStyleSheet = @import("../cssom/CSSStyleSheet.zig");
 const NodeIterator = @import("node_iterator.zig").NodeIterator;
 const Range = @import("range.zig").Range;
 
+const CustomEvent = @import("../events/custom_event.zig").CustomEvent;
+
 const Env = @import("../env.zig").Env;
 
 const DOMImplementation = @import("implementation.zig").DOMImplementation;
@@ -110,13 +112,21 @@ pub const Document = struct {
         return try parser.documentGetDoctype(self);
     }
 
-    pub fn _createEvent(_: *parser.Document, eventCstr: []const u8) !*parser.Event {
-        // TODO: for now only "Event" constructor is supported
-        // see table on https://dom.spec.whatwg.org/#dom-document-createevent $2
+    pub fn _createEvent(_: *parser.Document, eventCstr: []const u8) !union(enum) {
+        base: *parser.Event,
+        custom: CustomEvent,
+    } {
         if (std.ascii.eqlIgnoreCase(eventCstr, "Event") or std.ascii.eqlIgnoreCase(eventCstr, "Events")) {
-            return try parser.eventCreate();
+            return .{ .base = try parser.eventCreate() };
+        }
+
+        // Not documented in MDN but supported in Chrome.
+        // This is actually both instance of `Event` and `CustomEvent`.
+        if (std.ascii.eqlIgnoreCase(eventCstr, "CustomEvent")) {
+            return .{ .custom = try CustomEvent.constructor(eventCstr, null) };
         }
-        return parser.DOMError.NotSupported;
+
+        return error.NotSupported;
     }
 
     pub fn _getElementById(self: *parser.Document, id: []const u8) !?ElementUnion {
diff --git a/src/browser/events/custom_event.zig b/src/browser/events/custom_event.zig
index 3bf8179f5..530eaf5c8 100644
--- a/src/browser/events/custom_event.zig
+++ b/src/browser/events/custom_event.zig
@@ -19,6 +19,7 @@
 const parser = @import("../netsurf.zig");
 const Event = @import("event.zig").Event;
 const JsObject = @import("../env.zig").JsObject;
+const netsurf = @import("../netsurf.zig");
 
 // https://dom.spec.whatwg.org/#interface-customevent
 pub const CustomEvent = struct {
@@ -55,6 +56,27 @@ pub const CustomEvent = struct {
     pub fn get_detail(self: *CustomEvent) ?JsObject {
         return self.detail;
     }
+
+    // Initializes an already created `CustomEvent`.
+    // https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/initCustomEvent
+    pub fn _initCustomEvent(
+        self: *CustomEvent,
+        event_type: []const u8,
+        can_bubble: bool,
+        cancelable: bool,
+        maybe_detail: ?JsObject,
+    ) !void {
+        // This function can only be called after the constructor has called.
+        // So we assume proto is initialized already by constructor.
+        self.proto.type = try netsurf.strFromData(event_type);
+        self.proto.bubble = can_bubble;
+        self.proto.cancelable = cancelable;
+        self.proto.is_initialised = true;
+        // Detail is stored separately.
+        if (maybe_detail) |detail| {
+            self.detail = try detail.persist();
+        }
+    }
 };
 
 const testing = @import("../../testing.zig");
diff --git a/src/browser/netsurf.zig b/src/browser/netsurf.zig
index 079dfc0cc..026f5ade2 100644
--- a/src/browser/netsurf.zig
+++ b/src/browser/netsurf.zig
@@ -106,7 +106,7 @@ inline fn strToData(s: *String) []const u8 {
     return data[0..c.dom_string_byte_length(s)];
 }
 
-inline fn strFromData(data: []const u8) !*String {
+pub inline fn strFromData(data: []const u8) !*String {
     var s: ?*String = null;
     const err = c.dom_string_create(data.ptr, data.len, &s);
     try DOMErr(err);
diff --git a/src/tests/dom/document.html b/src/tests/dom/document.html
index 6eb61f342..be95a0027 100644
--- a/src/tests/dom/document.html
+++ b/src/tests/dom/document.html
@@ -60,7 +60,7 @@
   let byTagNameAll = document.getElementsByTagName('*');
   // If you add a script block (or change the HTML in any other way on this
   // page), this test will break. Adjust it accordingly.
-  testing.expectEqual(20, byTagNameAll.length);
+  testing.expectEqual(21, byTagNameAll.length);
   testing.expectEqual('html', byTagNameAll.item(0).localName);
   testing.expectEqual('SCRIPT', byTagNameAll.item(11).tagName);
 
@@ -167,3 +167,23 @@
   acss.push(new CSSStyleSheet());
   testing.expectEqual(1, acss.length);
 </script>
+
+<script id=createEvent>
+    const event = document.createEvent("Event");
+
+    testing.expectEqual(true, event instanceof Event);
+    testing.expectEqual("", event.type);
+
+    const customEvent = document.createEvent("CustomEvent");
+    customEvent.initCustomEvent("hey", false, false);
+
+    testing.expectEqual(true, customEvent instanceof CustomEvent);
+    testing.expectEqual(true, customEvent instanceof Event);
+
+    testing.withError(
+        (err) => {
+            // TODO: Check the error type.
+        },
+        () => document.createEvent("InvalidType"),
+    );
+</script>