Text Diff Checker

Comparing two versions of the same text is a task that shows up constantly — reviewing an edit to a document, spotting what changed between two config files, or checking a colleague's tweak to a block of code. Eyeballing it is slow and error-prone. A diff tool does it instantly.

How it works

This tool performs a line-by-line comparison using a longest-common-subsequence algorithm — the same core idea behind the diff in git and code-review tools. It finds the longest run of lines the two texts share, then marks everything else as either added (present only in the changed version) or removed (present only in the original).

Reading the result

Removed lines are shown in red with a minus sign, added lines in green with a plus sign, and unchanged lines are left neutral. A summary tells you how many lines were added and removed at a glance.

Common uses

- Reviewing document revisions and contract changes - Comparing two versions of a config, JSON, or code file - Checking what a find-and-replace actually changed - Spotting accidental edits between two drafts

Everything is compared locally in your browser, so you can safely diff private documents, unpublished drafts, or code with secrets in it — nothing is uploaded.