Code compare

Diff any codebase.

Paste two versions of any code. Syntax-highlighted comparison with line numbers.

Original code
0 lines · 0 chars
Modified code
0 lines · 0 chars
Comparing… Code stays in your browser — never uploaded
Comparison results Code
Change 1 of 1
These files are identical
No code changes found. Every line matches between the two files.
Explain this diff in plain English
Pro summarises what your code change actually does. "Switched the auth flow from JWT to session cookies, added a rate-limit guard on the login endpoint, and renamed the user-id parameter for consistency."
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How does code comparison work?

ChangeChecks lets you compare code online for free, with syntax highlighting for 20+ languages and proper line-number gutters. Paste two versions of a function, a config file, or an entire module and see every change in a unified or split view. Auto-detection picks the language; you can override it from the dropdown if needed.

Most code-diff tools either require a developer setup or send your code to a server. ChangeChecks runs entirely in your browser — convenient when you are reviewing a snippet from a Slack message, comparing two versions of a config you copied out of a deployment system, or checking whether a colleague's edit broke a function you rely on. The diff engine is the same battle-tested algorithm Git uses, with character-level highlighting inside changed lines so you can spot the actual difference, not just the changed line.

If you have ever pasted two snippets into a code comparison tool and immediately closed the tab because of an ad-laden interface, this is the calmer alternative. No login, no upload, no wall of banners — just the diff.

Frequently asked questions

Is my code private?

Yes. Everything runs in your browser; the code never leaves your device.

Which languages are supported?

20+ languages, auto-detected with manual override. JavaScript, TypeScript, Python, Go, Rust, Ruby, Java, Kotlin, C, C++, C#, PHP, Swift, SQL, HTML, CSS, JSON, YAML, Markdown, and Bash all have full syntax highlighting.

Does it preserve indentation?

Yes. Whitespace is preserved exactly; you can toggle ignore-whitespace if you want a noise-free diff.

Can I switch between unified and split views?

Yes. Toggle between merged (single column with both sides) and side-by-side (split view) at any time.

Will it run on very long files?

Yes, though performance falls off above roughly 10,000 lines. For very large files, splitting the diff by directory or commit usually makes more sense.

Learn more

All how-to guides
Walkthroughs for every comparison tool in the suite.
For QA teams
Verify the change in a pull request matches the spec exactly.