Text Tools
Text Diff Checker
Compare two versions of a text line by line or word by word, see what was added or removed, and how similar they are.
About the Text Diff Checker
The Text Diff Checker compares two versions of a text and shows exactly what was removed (−, red), added (+, green) or kept the same. Compare by line for documents and code, or by word to see small edits inside a sentence, and see a similarity score at a glance.
What you can do with the Text Diff Checker
- Clear colours: Removed lines in red (−), added in green (+).
- Line or word mode: By line for documents and code, by word for small edits.
- Similarity score: See how alike the two versions are at a glance.
- Side-by-side input: Paste the old and new versions and compare instantly.
How the comparison works
The tool finds the longest sequence shared by both versions, the same idea used by version-control tools like Git. If a line is inserted near the top, only that line is marked as added, rather than every line after it showing as changed.
Lines or words?
"Compare lines" is best for code, lists and documents: an edited line shows as one removed line and one added line. "Compare words" highlights the exact words that changed inside the text, which suits essays, contracts and messages.
Hidden differences
Two lines that look identical can differ by a trailing space or a capital letter. "Ignore extra spaces" is on by default; switch on "Ignore capitals" too if capitalization doesn't matter.
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Frequently Asked Questions
Does it compare words or lines?
Both. Choose "Compare lines" or "Compare words".
Is my text uploaded?
No. The comparison runs entirely in your browser, which makes it safe for confidential documents.
How long can the texts be?
Up to a few thousand lines each. Very large documents may need to be compared section by section.
How do I compare two versions of a document online?
Paste the older text into the Original box and the newer text into the Changed box. The result updates as you type: removed lines are marked with a minus in red, added lines with a plus in green, and the counts above show how many lines were added, removed or kept.
How is the similarity percentage worked out?
It is twice the number of matching lines (or words) divided by the total number of lines in both versions, times 100. In the sample, 2 of 4 lines match on each side, so 2 x 2 / 8 = 50% similar. It measures shared lines or words, not meaning.
Why does a line show as removed and added when I only changed one word?
In line mode a line counts as the same only if it matches exactly, so any edit makes it a removed line plus an added line. Switch to Compare words to see the exact words that changed inside the sentence.
How do I ignore differences in spacing or capital letters?
Turn on Ignore extra spaces to treat runs of spaces and leading or trailing spaces as equal, which is on by default. Turn on Ignore capitals so "Invoice" and "invoice" count as the same. Both toggles update the result immediately.
Can I use it to compare code or config files?
Yes. Line mode suits code, JSON, CSV and config files because each line is compared as a unit using the longest common subsequence, so an inserted line does not make every line after it look changed. Keep Ignore extra spaces off if indentation matters.
What does Swap sides do?
It moves the Changed text into the Original box and the Original text into the Changed box, then compares again. Added lines become removed lines and the other way round, which helps if you pasted the two versions into the wrong boxes.
How do I share or save the differences?
Use the Copy as diff button. It copies the comparison as plain text, with a plus before added lines, a minus before removed lines and two spaces before unchanged lines, so you can paste it into an email, chat message or ticket.
Is this useful for checking changes in a contract or agreement?
It is a quick way to spot wording that was added, removed or reworded between two drafts, such as a rent agreement or offer letter. Paste plain text, use Compare words for small edits, and still read the final version fully before you sign.
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