Monaco Diff Checker

Compare two pieces of code or text in a fast, VS Code-style diff editor that runs entirely in your browser. Spot every added, removed, and changed line at a glance — with full syntax highlighting, an order-aware diff engine, and one-click export.

Features

• VS Code-grade diff — powered by the Monaco editor, with inline change highlighting and synchronized scrolling.
• Side-by-side & inline views — switch layouts with one click.
• 10 built-in examples — one click loads a multi-language comparison and sets the matching syntax.
• 90+ languages, searchable — type to find any language Monaco supports (JavaScript, TypeScript, Python, Go, Rust, C#, SQL, YAML, Markdown, and many more). The list is generated from Monaco itself, so it's always complete.
• Both panels editable — paste or edit on either side and the diff updates live.
• Accurate stats — real added / removed / unchanged line counts and a similarity %, computed with a proper longest-common-subsequence algorithm (order-aware).
• Ignore whitespace / case — toggle to focus on meaningful changes (whitespace handling is per-line, so it never collapses your file into one line).
• File upload — load files into either panel (up to 2 MB).
• Change navigation — jump between differences with the Prev/Next buttons or F7/F8, with a live change counter.
• Export — copy a unified diff, download a .patch file, or share a URL with the comparison encoded in the link.
• Light & dark — follows your theme automatically.

How to use

1. Load content — pick from 10 ready-made Examples (JavaScript, Python, TypeScript, JSON, HTML, CSS, SQL, Java, Go, YAML — each switches the language automatically), paste into both panels, or upload files (Left / Right).
2. Pick a language — start typing in the language box and choose from the searchable list.
3. Compare — the diff and stats update automatically as you edit.
4. Navigate — use Prev/Next or F7/F8 to step through changes.
5. Share or export — Copy the unified diff, download a .patch, or Share a URL.

Keyboard shortcuts

• F8 — next difference
• F7 — previous difference

Privacy

All processing happens locally in your browser — nothing is uploaded to a server. When you use Share, the comparison is encoded in the URL hash fragment only.

Use cases

• Code review and pull-request comparison
• Before/after refactoring analysis
• Config / JSON / YAML comparison
• Log and debug-output comparison
• Version comparison and merge-conflict triage

FAQ

Which languages are supported? Every language the Monaco editor ships with — 90+ — surfaced through a searchable picker.

Is my code sent anywhere? No. The diff runs entirely client-side; share links keep data in the URL fragment, which browsers never send to the server.

How is similarity calculated? From the line-level longest-common-subsequence: unchanged / (added + removed + unchanged), as a percentage.