Diff Checker

A diff checker that keeps your text private

Diff Checker shows you exactly what changed between two versions of a text. Paste the original on the left and the new version on the right, press Compare, and every difference is marked: removed lines in red, added lines in green, and changed lines side by side with the exact words that changed highlighted.

Online diff sites ask you to paste your work into someone else’s server. Diff Checker runs entirely in your browser, so contracts, config files, source code and private documents never leave your computer.

Line by line, and word by word

Most diff tools stop at whole lines, which makes a single changed word inside a long line hard to spot. Diff Checker compares lines first, then compares the words inside each changed line, so you see that “30 days” became “14 days” without reading the sentence twice.

Ignore what does not matter

Turn on Ignore whitespace to skip changes in indentation and spacing, which is handy after a code formatter has run. Turn on Ignore case when capitalisation does not count. Windows and Unix line endings are treated as equal, so a file copied between systems does not show every line as changed.

A clear summary and a real diff file

A summary shows how many lines were added, removed and left unchanged. Copy the result as a standard unified diff, the same format Git uses, or download it as a .diff file to attach to a ticket or apply as a patch.

Who uses it

• Developers comparing config files, API responses or two versions of a function.
• Writers and editors checking what changed between drafts.
• Legal and business teams spotting edits in contracts and policies.
• SEO and content teams comparing page copy before and after an update.

Press Ctrl+Enter to compare without reaching for the mouse.