What this is for
Any time you have two versions of the same text — an AI's first draft and its rewrite, your prompt's old output and a regenerated one, or a teammate's edited copy — this shows you exactly what changed instead of making you read both versions side by side and spot the differences yourself. Additions are highlighted, removals are struck through, and everything unchanged stays plain.
Word-level vs line-level
- Word-level (prose) compares word by word and keeps your original spacing intact. Use it for paragraphs, emails, articles — anywhere the wording itself is what matters.
- Line-level (code) compares whole lines at a time. Use it for code, config files, or anything where a line moving or a whole line changing is the meaningful unit, not individual words within it.
Picking the wrong mode for the content still works, it's just noisier — line mode on a rewritten paragraph will often mark the entire paragraph as one big removal-plus-addition instead of showing the specific words that changed.
Reading the summary
The line above the diff — "12 words added, 4 words removed — 31% changed" — is a plain-count summary, not a similarity score from any AI model. It counts the words or lines jsdiff classified as added or removed against the total, so you can tell at a glance whether you're looking at a light edit or a full rewrite before reading the highlighted text in detail.
FAQ
Does this call an AI model to compare the text?
No. The comparison is a deterministic text-diffing algorithm (the same family used by git diff), not an AI judgment call. It finds the shortest set of insertions and deletions that turns "Before" into "After" — nothing is interpreted or summarized by a model.
Is my text uploaded anywhere? No. Both texts stay in your browser the entire time. Nothing is sent to a server.
Why does a single word change sometimes highlight more than that one word? The diffing algorithm looks for the smallest overall edit, which occasionally groups a changed word together with adjacent punctuation or spacing to keep the result readable rather than fragmenting it into tiny pieces.
Can I diff code with this? Yes — switch to line-level mode. It isn't syntax-aware, but it will correctly show which lines were added, removed, or left untouched.