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Diff Checker

Compare code, text, and JSON payloads with Monaco Editor's advanced diff algorithm. 100% client-side & private.

Original Code
Modified Code
Original Code

Fast & Private Monaco-Powered Diff Checker

Compare two versions of code, configuration files, SQL queries, or text documents instantly. Powered by Monaco Editor’s Advanced Diff Algorithm (the same engine behind VS Code), our diff checker detects character-level modifications, structural block movements, and refactorings without false positives.

  • Advanced AST-Aware Diffing: Intelligently matches nested blocks, indentation, and braces rather than naive line-by-line subtraction.
  • Split & Inline Modes: Switch seamlessly between side-by-side comparison and unified inline view.
  • 18+ Syntax Highlighters: Full syntax highlighting for JavaScript, TypeScript, JSON, HTML, CSS, SQL, Python, Markdown, Go, Rust, and more.
  • 100% Client-Side & Offline: Your code, proprietary algorithms, and sensitive tokens never leave your browser.
  • Export Standard Patches: Download standard unified .patch / .diff files compatible with Git and Unix patch.

How to Compare Code & Text

Compare differences in 3 simple steps:

  1. Paste or Upload: Insert your original text on the Left and modified text on the Right, or click the file upload icon.
  2. Inspect Differences: Jump through changes with the Previous / Next Change buttons, toggle Trim Spaces or switch between Split and Inline views.
  3. Export or Copy: Download the unified .patch file or copy the modified text directly to your clipboard.

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Frequently Asked Questions

Standard diff tools rely on simplistic line-by-line subtraction which often shifts closing braces or HTML tags incorrectly. Monaco's Advanced Diff Algorithm uses AST-inspired structural matching and heuristic alignment to produce cleaner, human-readable comparisons.

No. All diff comparisons, AST computations, character-level highlights, and patch generations run 100% locally in your browser. No files, tokens, or proprietary source code are ever uploaded or transmitted.

Yes! You can download a unified .patch / .diff file with one click, fully compatible with 'git apply', GitHub PR patches, and Unix patch(1).

Yes. Once the page is visited, Monaco Editor and its workers are cached by the service worker, allowing you to compare code and text even without an active internet connection.

It supports syntax highlighting for over 18 languages including JavaScript, TypeScript, JSON, HTML, CSS, SQL, Python, Markdown, Go, Rust, C/C++, Java, PHP, GraphQL, YAML, XML, and Shell scripts.

Split view displays Original (Left) and Modified (Right) side-by-side with synchronized scrolling. Inline view shows a single consolidated document with inline green additions and red deletions.