What is a Compare Text tool?

Compare Text (also called a diff tool or text comparison tool) highlights the differences between two versions of a piece of writing or code. Instead of reading both versions line by line and trying to spot the changes yourself, a diff tool shows you exactly what was added, removed or modified.

This is invaluable for writers revising a draft, developers reviewing a code change, editors tracking revisions, and students comparing their work against a reference.

How our diff works

We use the Myers diff algorithm — the same family of algorithms used by Git, GitHub, and most version control systems. It finds the shortest sequence of insertions and deletions needed to transform one text into another.

Green lines — content that was added in the changed version
Red lines — content that was removed
Yellow lines — lines that exist in both versions but with modifications; the specific changed words are highlighted within the line

Changed lines are detected when two lines are at least 35% similar by token overlap. Below that threshold, they appear as separate additions and removals — matching how Git shows diffs.

Common uses

Writers & editors — compare draft revisions to see exactly what changed between versions.
Developers — compare code snippets, config files, or API responses.
Legal & contracts — spot differences between two versions of a contract or agreement.
Translators — verify that the translated version faithfully reflects the source.
Students — compare submitted work against feedback or reference solutions.

Options explained

Ignore whitespace — treats multiple spaces as one, and trims leading/trailing whitespace. Useful when comparing text that has different indentation but identical content.
Case sensitive — when off, "Hello" and "hello" are treated as identical.
Hide unchanged lines — collapses long runs of identical lines to a single "N unchanged lines hidden" notice, keeping the diff focused on what actually changed.

Privacy

All comparison runs locally in your browser. Your text is never sent to a server. Nothing is stored after you close the tab (unless you have "Auto-save" enabled in the Word Counter — which is a separate tool).