Diff checker — compare two texts line by line
Paste two versions and see exactly what changed — line by line, with additions and deletions marked. Useful for contract revisions, copy edits and configuration files.
Runs in your browser — your input is not uploaded to ToolsNow.
How to use
- Paste the original. On the left, the version you are comparing against.
- Paste the changed version. On the right. The comparison runs immediately.
- Read the result. Green lines marked + were added, red lines marked − were removed. Line numbers for both versions run down the side.
- Reduce the noise. Ignore case or whitespace, or show only the lines that changed, when reformatting has muddied the comparison.
Questions
Does it compare word by word or line by line?
Line by line. That matches how developers and editors normally review changes, and it keeps long documents readable.
Is the diff the smallest possible?
Yes. It uses a longest-common-subsequence algorithm, which finds a provably minimal set of insertions and deletions rather than guessing with a heuristic.
Why does a reformatted paragraph show as entirely changed?
Because rewrapping changes every line. Switch on "Ignore whitespace" so lines that differ only in spacing are treated as equal.
Are my documents uploaded?
No. Both versions stay in your browser, making it safe for contracts and other confidential text.
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