In short: Two versions of a contract, an essay 'final_v2' versus 'final_FINAL', a config file that broke after edits: finding what changed by reading both is how errors survive. Paste both texts and see every added line in green and every removed line in red.
Updated August 28, 2026, after a fresh review, with updated visuals and links.
Comparison runs line by line with a proper LCS algorithm, the same family of logic Git uses, entirely in your browser.
What the diff shows
Identical lines appear dimmed; removals appear red with a minus prefix, additions green with plus. The summary line counts unchanged, added and removed lines so a 'small edit' of 200 changes gets caught immediately.
The algorithm finds the longest common subsequence between the two line lists: the minimal honest explanation of how text A became text B, rather than a naive position-by-position mismatch that flags everything after the first edit.
Because computation is quadratic in line count, the tool caps at 400 lines per side, which covers essays, contracts, configs, and articles comfortably. Repository-sized comparisons belong in Git.
Worth remembering
- Normalize before comparing: paste both texts through the case converter or trim trailing whitespace, otherwise cosmetic noise hides the real edits.
- For documents someone emailed back, copy from the Word/PDF into plain text first so formatting does not invent phantom changes.
Frequently asked
Does it compare word by word?
This tool works line by line, which suits code, lists and prose paragraphs. For word-level comparison inside a single changed paragraph, a dedicated word-diff tool (or Git with color-words) is sharper.
Is my text uploaded anywhere?
No. The comparison runs fully in your browser tab with JavaScript; close the tab and nothing remains. That is what makes it safe for contracts and drafts.
Find every related tool in our Developer Tools: Every Free Utility index.
