Text Diff Checker
Paste an original and a changed version of some text to see exactly which lines were added, removed or left the same — useful for spotting edits in documents, emails or config files.
How it works
The two texts are compared line by line using a longest-common-subsequence approach: the tool finds the longest run of lines that appear unchanged in the same order in both versions, then marks everything else as added (in the changed version) or removed (from the original).
Worked example
Paste a paragraph on the left, then paste a lightly edited version on the right — the tool marks the untouched lines as unchanged and highlights only the lines that actually differ.
For the clearest results, keep each logical change on its own line — the comparison is more precise when a sentence or item is one line rather than wrapped across several, since matching happens line by line.
Common questions
Does this compare word by word or line by line?
Line by line. Each line is matched against the other version, and lines that don’t match are marked as added or removed.
Why does one small edit show a whole line as changed?
Because the comparison works at the line level — editing one word inside a line marks that whole line as removed and its replacement as added, rather than highlighting the single word.
Can I compare code with this?
Yes, it works for any plain text, including code, though it isn’t syntax-aware.
Is either version of my text sent anywhere?
No, the comparison runs entirely in your browser.
What’s a good use for this besides checking documents?
Comparing two versions of a contract clause, checking what changed between two drafts of an email before sending, or spotting exactly what a colleague edited in a shared document are all common uses — anywhere you have "before" and "after" text and want to know precisely what moved.