Don's Tools · Developers · Diff Checker

Diff checker

See exactly what changed between two versions of text or code, right in your browser. Nothing is uploaded.

Works offline: both texts are compared in your browser with nothing uploaded. The diff is line by line: lines only in A are removed (red), lines only in B are added (green), unchanged lines are grey.
Diff Checker is a free developer tool that compares two texts or code snippets entirely in your browser, with nothing uploaded. It shows the differences line by line, marking removed lines in red, added lines in green and unchanged lines in grey, with options to ignore case, whitespace and trailing spaces, and lets you copy the resulting diff.

Frequently asked questions

Is my text uploaded anywhere?

No. Both versions are compared entirely in your browser and are never uploaded, so even private code or documents stay on your device.

How does the comparison work?

It compares the two texts line by line using a shortest-edit algorithm. Lines only in the original are marked removed in red, lines only in the changed version are added in green, and matching lines are grey.

What do the ignore options do?

Ignore case treats capitals as the same, Ignore whitespace ignores differences in spaces and tabs, and Trim line ends ignores trailing spaces, so only meaningful changes show up.

Can I save the differences?

Yes. After comparing, copy the diff, where added lines start with a plus, removed lines with a minus and unchanged lines are indented.

Is there a size limit?

Each side can be up to about 4000 lines; larger inputs are best compared in smaller sections so your browser stays responsive.