Compare two texts right in your browser
Paste the original text on the left and the changed version on the right — the tool instantly shows every added (green) and removed (red) line, side by side or inline, with line numbers and word-level highlights. Everything runs locally in your browser: no upload, no signup, works offline.
Why compare locally instead of uploading?
The texts people diff are often the most sensitive ones: contract versions, offers, source code, configuration files. Many popular diff websites process your input on their servers — a real problem once customer data or unreleased code is involved. This tool transmits nothing: the entire comparison runs on your device, which also makes it GDPR-friendly by design.
How does the comparison work technically?
First the tool computes a line-based diff using the Myers algorithm — described in 1986 in Eugene W. Myers' paper "An O(ND) Difference Algorithm and Its Variations" (Algorithmica, 1986); the same family of algorithms powers Git's default diff. Each changed line pair is then refined with a word-level diff: you see not just that a line differs, but which words changed inside it. For performance, the word diff only runs on paired changed lines — it is skipped for extremely long lines and very large change blocks so the page stays responsive.
What do the options do?
- Ignore case — "Hello" and "hello" count as equal. Handy when only capitalization was normalized.
- Ignore whitespace — leading and trailing spaces or tabs on each line are ignored. Ideal after reformatting or indentation changes.
- Side by side / Inline — the side-by-side view suits wide screens and direct line comparison; the inline view (removed lines first, then added lines per block) is easier to read on mobile.
How large can the texts be?
There is no hard limit. Above roughly 1 MB of combined input, the tool shows a warning: very large, very different texts can take noticeable compute time in a browser. As a safeguard, the diff computation aborts after a time limit and falls back to a simplified comparison (all old lines removed, all new lines added) instead of freezing the tab. Everyday documents, contracts and source files are nowhere near that point.
Does the comparison stay private?
Yes. Both texts stay on your device; at most they are stored locally in your browser so your inputs are still there on your next visit (skipped for very large texts). There is no server that ever sees your text.