Diff Checker
Compare two blocks of text or code and see exactly what changed. Character-level diffs, syntax highlighting, file uploads, and export to .diff -- all free, no login required.
How This Diff Checker Works
Put the original on the left and the modified version on the right. Or drag-and-drop files directly.
The LCS algorithm finds the longest common subsequence and identifies every addition, deletion, and change.
See line-by-line and character-level diffs. Switch between side-by-side, unified, or inline views.
Copy the diff to clipboard or download as a standard .diff file for code reviews and version control.
What Makes This Different
No Login Required
Unlike diffchecker.com, you never need to create an account or sign in.
Character-Level Diffs
See exactly which characters changed within a line, not just that the line changed.
Syntax Highlighting
Support for JavaScript, JSON, HTML, CSS, Python, and SQL -- free, not behind a paywall.
100% Private
Everything runs in your browser. Your code never touches our servers.
File Upload
Drag and drop any text file directly into the editor. No size limits.
Export to .diff
Download standard diff format files for code reviews and version control workflows.
Frequently Asked Questions
How does the diff algorithm work?
This tool uses a Longest Common Subsequence (LCS) based algorithm. It compares two texts line by line, finds the optimal alignment, then highlights additions, deletions, and character-level changes within modified lines.
Is my data sent to a server?
No. The entire diff computation runs in your browser using JavaScript. Your text and code never leave your device. There are no servers, no logging, no tracking.
Can I compare files directly?
Yes. Drag and drop any text-based file (.txt, .js, .py, .json, .html, .css, .sql, etc.) into either textarea. The tool reads the file locally and loads the content for comparison.
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