Text Difference Checker
Compare two texts line by line and see exactly what was added, removed and left alone, with a similarity score.
Fill in the form and press “Compare” to see the result here.
How to use it
- 1Paste the original text in the first box.
- 2Paste the version you want to compare in the second box.
- 3Turn on the ignore options if case or spacing changes are noise for you.
- 4Press Compare to see the line-by-line difference.
About the Text Difference Checker
The comparison uses a longest-common-subsequence diff, the same family of algorithm as the one in version control. It finds the largest set of lines the two versions share and reports everything else as added or removed.
Ignoring whitespace is useful when comparing code or JSON that has been reformatted: it removes the indentation noise so only the real changes show.
Each side is limited to 4,000 lines. The algorithm compares every line against every line, so the work grows with the square of the input and a larger comparison would lock up the page.
Questions people ask
Does it highlight changes within a line?
No - the comparison is per line. A line with a single changed word shows as one removal and one addition, which keeps the output readable on long documents.
Is your text uploaded to a server?
No. This tool runs entirely in your browser using standard web APIs, so your text never leaves your device. You can confirm it by opening your browser's network panel while the tool runs, or by disconnecting from the internet after the page has loaded.
Is it free, and do I need an account?
Yes, it is free, and there is no account, no sign-up and no watermark on the result. The project is funded by optional donations.