Diff Checker
Compare two blocks of text and see additions and deletions highlighted.
About this tool
Whether you're reviewing a draft, comparing two versions of a document, or figuring out what actually changed between two pieces of text, eyeballing two blocks side by side is slow and error-prone. This tool computes a diff and highlights additions and deletions, with a choice between line-level (good for structured text) and word-level (good for prose) granularity.
Under the hood, diff tools look for the longest common subsequence between two texts: the largest set of content that appears in both, in the same order. Everything outside that shared backbone is marked as removed from the original or added in the changed version. This is the same basic approach used by version-control tools like Git, which is why the output looks familiar if you've reviewed code changes.
Useful everyday comparisons include checking what an editor changed in a draft, spotting differences between two versions of a contract clause, comparing configuration files, or confirming that two long lists match. If a diff looks noisier than expected, try the other granularity: word diff is much clearer for edited prose, while line diff is cleaner for lists, code, and data.
Frequently asked questions
- Line diff versus word diff: which should I use?
- Line diff is generally better for structured text, where whole lines change together. Word diff is better for prose, where a single word changing shouldn't highlight the entire surrounding sentence as different.
- Does this send my text anywhere to compare it?
- No, the diff is computed entirely in your browser using a client-side diffing library. Neither block of text is sent to a server.
- Why is a whole line highlighted when I only changed one word?
- In line diff mode, any change to a line marks the entire line as removed and re-added. Switch to word diff to see exactly which words changed within a line.
- Does whitespace count as a difference?
- Yes. Extra spaces, tabs, or a different line ending all count as changes. If two texts look identical but show differences, invisible whitespace is the usual cause.