Text Compare
Compare two texts line by line and see exactly what changed.
How to use the Text Compare
- Paste the original text on the left.
- Paste the changed version below it.
- Read the highlighted differences and the similarity score.
About the Text Compare
Text Compare is a line-by-line diff tool. Paste an original (Text A) and a changed version (Text B) and it lines them up, marking each line as unchanged, added in B, or removed from A. It finds the alignment with a longest-common-subsequence algorithm — the same idea behind the diffs in version-control tools — so it correctly matches the lines that stayed the same even when others are inserted or deleted around them.
It also reports a single similarity percentage. That figure is the longest common subsequence of the two texts’ word sequences, measured against their combined length, so it rewards not just shared words but shared word order. Two texts with the same sentences in the same order score high; the same words shuffled score lower. Everything happens in your browser, so both versions stay on your device.
Be clear about what this is not. It compares the two texts you give it and nothing else. It does not search the web, check for plagiarism, or detect AI-written content — a high or low score says only how similar your two inputs are to each other. To tidy or measure text before comparing, a word counter or the text summarizer can help.
Frequently asked questions
Is this a plagiarism or AI detector?
No. It only compares the two texts you paste. It does not search the internet, check your text against any database, or judge whether it was written by AI. The result reflects your two inputs alone.
How is the similarity percentage calculated?
It takes the longest common subsequence of the two texts’ word sequences and measures it against their total combined length. Because a subsequence keeps order, the score reflects shared wording and the order it appears in, not just a bag of common words.
Does it compare by line or by word?
Both. The visible diff of added, removed and unchanged rows is line by line, while the similarity percentage is computed over words, so small edits within a line still register.
Will reordered paragraphs show as changed?
Often yes. Because matching follows sequence order, moving a block can appear as a removal in one place and an addition in another, even though the words themselves are identical.
Does my text get uploaded?
No. The comparison runs entirely in your browser; neither version is sent to a server or stored.