diff --git a/packages/utils/src/audit-diff-finder.js b/packages/utils/src/audit-diff-finder.js
index 231ced94a..43a7d258e 100644
--- a/packages/utils/src/audit-diff-finder.js
+++ b/packages/utils/src/audit-diff-finder.js
@@ -242,6 +242,15 @@ function findAuditDetailItemKeyDiffs(auditId, baseEntry, compareEntry) {
 
   return diffs;
 }
+
+/** @param {string} s */
+function replaceNondeterministicStrings(s) {
+  return s
+    .replace(/\b[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\b/gi, 'UUID')
+    .replace(/:[0-9]{3,5}\//, ':PORT/')
+    .replace(/\.[0-9a-f]{8}\.(js|css|woff|html|png|jpeg|jpg|svg)/, '.HASH.$1');
+}
+
 /**
  * TODO: consider doing more than URL-based comparisons.
  *
@@ -255,7 +264,7 @@ function zipBaseAndCompareItems(baseItems, compareItems) {
       ...baseItems.map((item, i) => ({item, kind: 'base', index: i})),
       ...compareItems.map((item, i) => ({item, kind: 'compare', index: i})),
     ],
-    entry => (entry.item.url === undefined ? JSON.stringify(entry.item) : entry.item.url)
+    entry => replaceNondeterministicStrings(getItemKey(entry.item))
   );
 
   /** @type {Array<{base?: DetailItemEntry, compare?: DetailItemEntry}>} */
@@ -453,4 +462,5 @@ module.exports = {
   getRowLabelForIndex,
   getMostSevereDiffLabel,
   zipBaseAndCompareItems,
+  replaceNondeterministicStrings,
 };
diff --git a/packages/utils/test/audit-diff-finder.test.js b/packages/utils/test/audit-diff-finder.test.js
index 6aa00a56f..731769fa3 100644
--- a/packages/utils/test/audit-diff-finder.test.js
+++ b/packages/utils/test/audit-diff-finder.test.js
@@ -13,6 +13,8 @@ const {
   getDiffLabel,
   getRowLabel,
   getRowLabelForIndex,
+  zipBaseAndCompareItems,
+  replaceNondeterministicStrings,
 } = require('@lhci/utils/src/audit-diff-finder.js');
 
 describe('#findAuditDiffs', () => {
@@ -516,3 +518,35 @@ describe('#getRowLabel', () => {
     expect(getRowLabelForIndex(diffs, 2, 0)).toEqual('better');
   });
 });
+
+describe('#replaceNondeterministicStrings', () => {
+  it('should work on non-replacements', () => {
+    expect(replaceNondeterministicStrings('nonsense')).toEqual('nonsense');
+    expect(replaceNondeterministicStrings('Other')).toEqual('Other');
+    expect(replaceNondeterministicStrings('Unknown')).toEqual('Unknown');
+    expect(replaceNondeterministicStrings('foo.notahash.js')).toEqual('foo.notahash.js');
+    expect(replaceNondeterministicStrings('foo.1234567.js')).toEqual('foo.1234567.js');
+    expect(replaceNondeterministicStrings('at foo.js:1234')).toEqual('at foo.js:1234');
+    expect(replaceNondeterministicStrings('http://localhost/foo')).toEqual('http://localhost/foo');
+    expect(replaceNondeterministicStrings('data:image/png;base64,abcdef')).toEqual(
+      'data:image/png;base64,abcdef'
+    );
+  });
+
+  it('should replace hash parts', () => {
+    expect(replaceNondeterministicStrings('foo.12345678.js')).toEqual('foo.HASH.js');
+    expect(replaceNondeterministicStrings('foo.abcdef12.js')).toEqual('foo.HASH.js');
+  });
+
+  it('should replace ports', () => {
+    expect(replaceNondeterministicStrings('http://localhost:1337/foo?bar=1#baz')).toEqual(
+      'http://localhost:PORT/foo?bar=1#baz'
+    );
+  });
+
+  it('should replace uuids', () => {
+    expect(
+      replaceNondeterministicStrings('<a href="/app/12345678-1234-1234-1234-123456781234">Text</a>')
+    ).toEqual('<a href="/app/UUID">Text</a>');
+  });
+});