Compare two texts and highlight added, removed and unchanged lines
A diff checker compares two pieces of text and highlights exactly what changed between them — which lines were added, which were removed and which stayed the same. Instead of reading two versions side by side and trying to spot the difference by eye, you get a colour-coded view that points straight to it. This is how code review, version control and document collaboration work under the hood: every change is expressed as a precise set of additions and deletions rather than "something is different somewhere".
The comparison works by aligning the two texts and finding the smallest set of edits that turns one into the other, so unchanged sections line up and only real differences stand out. That makes a diff invaluable for catching a single altered value buried in a long config file, confirming what a colleague edited in a contract, or understanding why two outputs that "should be identical" are not. This tool runs the comparison in your browser, so the text you paste is never uploaded.
It aligns the texts by line first, then highlights changes within them, so you see both which lines changed and what changed inside each line. This matches the model used by tools like Git and code review platforms.
Invisible characters are the usual cause: trailing spaces, tabs versus spaces, or different line endings (Windows CRLF versus Unix LF). A diff is exact, so it flags differences your eye cannot see — which is precisely what makes it useful.
Yes. Any plain text works — source code, JSON, YAML, CSV, logs or prose. It is especially handy for config files, where a single changed flag can be hard to find manually.
No. The comparison runs entirely in your browser, so neither version is uploaded. You can safely diff proprietary code, private documents or sensitive data.
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