Spot what changed between two versions
Somebody updated the config file and now the app is broken. You’ve got the old version and the new version. Instead of reading both line by line with your eyes glazing over, paste them side by side here. Green = added, red = removed, white = unchanged. Same idea as git diff, but you don’t need a repo or a terminal.
Uses the LCS (Longest Common Subsequence) algorithm, the same approach Git and Unix diff use. Line numbers are included so you can reference specific changes.
Paste, compare, done
Left side: original text. Right side: modified text. Click compare. The diff appears with color coding. Works with anything that’s text, code, YAML configs, SQL scripts, Markdown docs, CSV data, log files, legal contracts, whatever.
Real-world uses
Config debugging: the staging environment works, production doesn’t. Diff the two config files and the change that broke things jumps out immediately.
Code review without Git: sometimes you’re comparing code snippets from a chat message, a forum post, or a Google Doc. No repo, no PR, just two versions of something you need to compare.
Merge conflict resolution: paste both sides of the conflict and actually see what’s different before choosing which version to keep.
Deployment checks: diff your staging and production environment variables. One missing API_KEY entry and your whole deploy fails.
Database migrations: two versions of a stored procedure or migration script, side by side, so you can verify the change is correct.
About the algorithm
LCS finds the longest sequence of lines that appear in both texts in the same order. Lines in the common subsequence are “unchanged.” Lines only in the original are “removed.” Lines only in the modified version are “added.” It’s the gold standard for text comparison, the same approach GitHub, GitLab, and Bitbucket use in their PR diffs.
For structural JSON comparison (key-level changes instead of line-level), try the JSON Diff Checker instead.
FAQ
Can it handle large files?
Yes, though very large documents (thousands of lines) may take a moment depending on your device. It’s all processed locally.
Character-level diff?
It’s line-level comparison. You’ll see which lines changed, but differences within a single line need visual inspection.
Is it safe for sensitive data?
Everything runs client-side in JavaScript. No data gets sent to any server. Safe for proprietary code, credentials, internal docs.