Text Diff Checker
Compare two blocks of text and see exactly what was added, removed, or left unchanged.
Enter text in both fields to see the differences.
This tool finds differences using the longest common subsequence, an algorithm that identifies the largest set of characters both texts share in the same order and treats everything else as an insertion or a deletion. It is the same underlying idea used by most code diff tools, applied here at the character level.
Character-level diffing highlights every small edit and suits prose, contracts, or short passages, while line-level diffing compares whole lines at once and suits source code, where a single changed character usually means the entire line was rewritten.
Read the result the way a reviewer reads a marked-up page: text flagged as removed once occupied the spot where an insertion now stands, and anything unmarked was identical in both versions. Skimming only the highlighted lines lets you review a long document in seconds, and because the comparison is exact, a clean diff is strong evidence that two versions truly match.
Common uses
- Reviewing two drafts of a contract or marketing copy side by side to pinpoint exactly which clauses or phrases were edited between versions.
- Checking exactly which words an AI rewrite changed in a paragraph, so you can confirm the meaning was preserved rather than reading the whole thing again from scratch.
Frequently asked questions
- Is this a line-by-line or character-by-character diff?
- It compares character by character for typical inputs, but automatically switches to line-by-line comparison for very long text to keep the browser responsive.
- Does it detect moved paragraphs?
- No—the algorithm has no concept of "moved" text. A paragraph relocated elsewhere is shown as a deletion at its old position and an insertion at its new one.
- Does my text leave the browser?
- No. Both text boxes are compared entirely on your device using JavaScript; nothing is uploaded to any server.