Text Diff Checker
Free online text diff checker. Compare two texts, highlight additions, deletions, and changes. Line-by-line and word-by-word diff. Works offline.
About this tool
Compare two texts side by side and see exactly what changed. Supports line-by-line diff and word-by-word diff for changed lines. Additions are highlighted in green, deletions in red, and modifications in yellow. Features include swap texts, copy unified diff output, stats summary, and localStorage persistence. Uses LCS algorithm for accurate diff computation.
Details
- Category
- Utilities
- Version
- 1.0.0
- Size
- 10 KB
- Updated
- Jun 2026
Frequently Asked Questions
How does the diff algorithm work?
It uses LCS (Longest Common Subsequence) to find matching lines, then marks adjacent additions and deletions as changes. For word diff, the same algorithm runs on individual words within changed lines.
What do the colors mean?
Green lines are additions (exist in modified but not original). Red lines are deletions (exist in original but not modified). Yellow lines are modifications (changed content).
Can I copy the diff output?
Yes. Click Copy Diff to get a unified diff format with + and - prefixes.
Is my text sent anywhere?
No. All diff computation happens locally in your browser. Nothing leaves your device.