Tools / Text Diff Checker
Text Diff Checker
Compare two blocks of text side by side and see exactly what changed — line by line — right in your browser.
Removed lines are highlighted red, added lines green. Comparison happens locally in your browser.
// About this tool
Text Diff Checker
This diff checker compares two blocks of text and highlights the exact lines that differ, side by side. Added lines appear green, removed lines red, and unchanged lines are shown in plain text — so you can see precisely what changed between two versions.
It uses a longest-common-subsequence line diff, the same approach git uses, so it stays aligned even when lines are added or removed mid-file.
Everything runs locally in your browser. Nothing you paste is uploaded, and the tool works fully offline.
// When to use it
Review a config change before applying it
Paste the old and new versions of a config or settings file and confirm only the intended lines changed.
Compare two versions of code
Drop in two versions of a file to see which lines were added or removed without opening a terminal.
Check a doc or copy edit
Compare original and edited text to confirm the exact wording changes before publishing.
// Questions
Is my text sent to a server?
No. The diff is computed entirely in your browser. Nothing is uploaded, and the tool works offline.
Is it line-level or character-level?
Line-level. It highlights whole lines that differ, aligned with a longest-common-subsequence diff so added and removed lines stay paired.
Can it handle large blocks?
It handles typical file-sized blocks easily, since the diff runs locally. Extremely large inputs are limited by browser memory.
Does it match git's diff output?
It uses the same LCS alignment approach git uses, shown in a side-by-side view rather than unified output.
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