Code Compare & Diff Tool
Modified Code
Diff Review
Accept or reject each change individually.
0/0
Merged Result
Edit the final output before copying.Common ancestor (base)
Syntax Preview
Fast local highlighting for review readability.Why Use DiffMergy’s Code Compare & Diff?
Whether you are reviewing a pull request, debugging a regression, or auditing a codebase migration, DiffMergy’s Code Compare gives you a precise, color-coded view of every change between two code versions. With 30+ language modes, word-level diff highlighting, and an intuitive accept/reject workflow, it is the fastest way to understand what changed without leaving your browser.
Unlike cloud-based alternatives, all comparison logic runs locally using a custom diff engine optimized for accuracy. There are no file size limits, no upload queues, and no privacy concerns. Simply paste your code and see the diff instantly.
Key Features
- Real CodeMirror 6 editor with line numbers, code folding, bracket matching, auto-indent, and multi-cursor editing
- Side-by-side and unified diff views with word-level change highlighting inside the editor
- Three-way merge (base, ours, theirs) with conflict markers and one-click conflict resolution
- Command palette (Ctrl+K) for keyboard-first navigation across every tool
- Accept or reject individual changes with full undo/redo history
- Automatic move detection for refactored or relocated code blocks
- Handles very large files with virtualized diff rendering
- 30+ programming languages with syntax highlighting
- Compare by pasting, uploading files, or fetching a URL
- Share comparisons via compressed link, export unified .patch files, and save sessions locally
100% Private — No Server Upload
All processing happens entirely in your browser using modern browser APIs. Your sensitive source code, credentials, and files never leave your device — no servers, no databases, no tracking, no sign-up required.
Fast & Reliable
Built with vanilla TypeScript and a lightweight custom engine, DiffMergy delivers sub-millisecond processing with zero network latency. The entire toolkit works on any modern browser across all operating systems, with no installation or setup needed.
Frequently Asked Questions
How do I compare two files with DiffMergy?
Open Code Compare on the home page, paste or upload your original code in the left editor and the modified version in the right editor. Select the appropriate language from the dropdown, then click Compare or press Ctrl+Enter to see the highlighted diff.
Is DiffMergy really private?
Yes. All processing — diffing, syntax highlighting, formatting, and merging — happens entirely in your browser using local JavaScript. No data is ever sent to any server, stored in a database, or logged.
What programming languages does DiffMergy support?
DiffMergy supports 30+ programming languages including JavaScript, TypeScript, Python, Java, C#, C++, Go, Rust, Ruby, PHP, Swift, Kotlin, SQL, HTML, CSS, JSON, YAML, and many more.
Can I save my comparison and come back later?
Yes. Click the Save button to store your current session in your browser’s local storage. Sessions are also auto-saved every 30 seconds. Click Load to restore any saved session.
How do I open the command palette?
Press Ctrl+K (or Cmd+K on Mac) on any page to open the command palette. Type to fuzzy-search every tool and action, then press Enter to run it. Use the arrow keys to move and Escape to close.
Does DiffMergy support three-way merge?
Yes. In the Merged Result panel switch the merge mode to 3-way and paste the common ancestor (base) version. DiffMergy merges your version and the other version, flags conflicts with standard <<<<<<< / ======= / >>>>>>> markers, and lets you resolve them with Keep Ours or Keep Theirs.