Compare two versions of a text line by line and see what changed. Runs entirely in your browser.
How the text diff works
Paste two versions of a text and press Compare. Lines that appear only in the original are marked red, lines only in the changed version green, and unchanged lines plain. It uses a longest-common-subsequence algorithm, the same idea behind code review diffs, computed in your browser.
Frequently asked questions
Does it compare words or lines?
Lines. For paragraph-level edits that is the clearest view; reformat spacing if you want a finer comparison.
Is my text uploaded?
No. The comparison runs entirely in the page.
Is there a size limit?
The diff runs on your device, so very large texts are limited by the memory your browser has free.
How to use it
- Paste your original text into the first input field labelled “Paste the original…”.
- Paste the revised text into the second input field labelled “Paste the changed version…”.
- Click the Compare button.
- Review the result below: red lines exist only in the original, green lines exist only in the changed version, and plain lines are identical in both.
Where it comes in handy
A technical writer revises a 450-word support article and wants to identify which sentences were reordered or reworded. Pasting the old and new drafts into the two fields shows each modified line in green or red, making a 12-line edit traceable in seconds.
A developer compares a 200-line configuration file after a deployment change. Lines removed by the new config appear in red, newly added parameters in green, and the unchanged boilerplate in plain text, so only the 18 affected lines need manual review.
A translator checks a 1,200-word document where only paragraph 3 was updated. Feeding both versions into the tool highlights the altered paragraph and leaves the other 47 paragraphs as plain unchanged lines, saving time compared with scrolling through the full text.
Worth knowing
- The comparison works at the line level, not the word level. If you paste a single long paragraph without line breaks, the entire block counts as one line and the diff may show nothing even though the wording changed inside it.
- The algorithm normalises consecutive spaces to a single space before comparing, so extra indentation or spacing changes are invisible in the output.
- Performance depends on your browser’s available memory. Inputs over roughly 10,000 lines per field may cause the page to lag or become unresponsive on lower-spec devices.