Diff Checker
Paste an original and a changed version to see a line-by-line diff with additions and removals highlighted. Nothing you paste leaves your browser.
Paste text in both boxes to compare.
How to use this tool
- Paste the original text on the left and the changed version on the right.
- Read the combined diff: green lines were added, struck-through red lines were removed.
- Check the summary count of added and removed lines at the top.
How it works
The tool computes a longest-common-subsequence (LCS) diff — the same core algorithm behind git diff. It finds the largest set of lines the two texts share in order, then marks everything else as added or removed, which produces the minimal line-level change set.
Within each changed line pair, a second word-level LCS pass highlights exactly which words changed. View results inline or side by side, collapse long unchanged stretches, and copy a standard unified diff (with @@ hunk headers) that patch and code-review tools understand.
Line-level diffs are ideal for code, configs, and structured text. For prose, where a single edited word changes a whole line, word-level diffing (a future addition) highlights changes more precisely.
Frequently asked questions
How do I compare two documents?
Paste one version in each box. The diff below shows exactly which lines changed — green for additions, red strikethrough for removals — with unchanged lines for context.
Why does one small edit show as a remove plus an add?
This is a line-level diff: a changed line counts as the old line removed and the new line added, just like git. That's normal and expected.
Is there a size limit?
Very large texts (millions of line-pair comparisons) are declined to keep the page responsive — split them into sections and compare in parts.