Text Diff
Compare two blocks of text and see exactly which lines changed.
Results appear here as soon as you start typing.
How to use Text Diff
Paste the original on the left
Any text works — code, prose, a CSV export, a log file.
Paste the changed version on the right
The comparison updates as you type. Nothing is uploaded.
Read the result
Removed lines are marked with a minus, added lines with a plus. Colour is never the only signal.
Why use this text diff
Runs on your device
Your input is handled entirely in this browser tab. Nothing is uploaded, so there is nothing for us to store, log or leak.
No sign-up, no quota
No account, no daily limit, no watermark and no email wall. Use it once or two hundred times a day.
Built to be linked
Options are stored in the URL, so a configured tool is a link you can send to a colleague or bookmark.
Technical notes
Comparison uses a longest-common-subsequence diff, the same approach as git, so a line inserted near the top does not mark every line after it as changed. Identical prefixes and suffixes are trimmed first, which is what keeps large files fast: two 20,000-line files differing in ten places skip more than 99% of the work.
Measured on our own test set
- 500 vs 500 lines, 2 edits
- 1.6 ms
- 5,000 vs 5,000, 20 edits
- 1.0 ms
- 2,000 vs 2,000, fully different
- 43.6 ms
i5-6300U, Chrome 151, median of 8
faster than the 500-line case — trimming the identical prefix and suffix skips almost the whole table
the genuine worst case, where nothing can be trimmed
Supported
- Line-level additions and deletions with original line numbers
- Mixed CRLF, LF and CR line endings
- Whitespace-insensitive and case-insensitive comparison
- Symbols as well as colour, so the result works with colour vision deficiency
Limits and trade-offs
- Line-level only. A one-character edit reads as a delete plus an add.
- Beyond about 2,000 differing lines on each side the comparison falls back to a whole-block replacement to avoid freezing the tab.
- Not a merge tool — it shows differences, it does not resolve them.
Last verified August 2026 · benchmarks re-run each quarter.
Frequently asked questions
How does the comparison work?
It computes the longest common subsequence of the two line lists, which is the same algorithm family that git diff uses. That finds the minimal set of insertions and deletions, rather than reporting everything after the first change as different.
Is my text uploaded anywhere?
No. The comparison runs entirely in your browser. That matters more here than on most tools, because people diff contracts, config files with credentials in them, and unreleased code.
How large can the two texts be?
Comfortably a few thousand lines each. Identical leading and trailing sections are trimmed before the comparison starts, so two 20,000-line files that differ in ten places compare almost instantly.
Does it show which characters changed within a line?
Not yet — this is a line-level diff. A line with one changed character shows as one removal and one addition. Word-level highlighting is on the roadmap.
Why do two lines that look identical show as different?
Almost always trailing whitespace, or a CRLF line ending meeting an LF one. Turn on "ignore leading and trailing spaces" to confirm; if the difference disappears, that was it.