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Comparing two versions of the same document by eye is slow and error-prone — a single changed word buried in a long paragraph is easy to miss. A proper line-by-line diff shows exactly what changed between two versions of text, the same way developers compare code changes.
This tool compares your original and revised text and shows every line as unchanged, added, or removed, plus an overall similarity percentage — useful for reviewing edits, comparing document revisions, or checking what changed between two drafts.
How it works
Paste your original text and your revised text into the two boxes. The tool compares them line by line using a standard longest-common-subsequence diff algorithm (the same technique version control tools use), then shows every line marked as unchanged, added, or removed, along with counts and an overall similarity percentage.
- Paste your original text.
- Paste your revised text.
- Click Compare and review the line-by-line diff.
Examples
Reviewing a single edited line
Changing one sentence in a three-paragraph document shows up as exactly one removed line and one added line, with everything else marked unchanged — making the actual edit immediately obvious.
Comparing two drafts
Pasting an early draft against a final version reveals a 40% similarity score along with every specific line that was reworded, added, or cut.
Who should use it
- Reviewing what changed between two drafts of a document.
- Checking edits made by a collaborator or editor.
- Comparing two versions of code, config, or other line-based text.
Industry applications
- Content editing and proofreading
- Legal and contract revision review
- Software documentation and code review
Advantages
- Uses a proper longest-common-subsequence algorithm, not a naive line-position comparison.
- Shows unchanged, added, and removed lines with clear counts and a similarity score.
- Works on any line-oriented text — prose, code, or structured content.
Limitations
- Compares whole lines, not individual words within a line.
- Sensitive to line-break differences between otherwise similar content.
- Doesn't merge or apply changes — it's a comparison tool, not an editor.
Common mistakes to avoid
- Expecting word-level highlighting within a line rather than whole-line addition/removal markers.
- Comparing text with inconsistent line breaks (e.g. one version wrapped differently), which can make similar content appear more different than it actually is.
- Overlooking the similarity percentage as a quick sanity check before reading the full line-by-line diff.
Best practices
- Normalize line breaks in both texts before comparing if one version was reformatted or re-wrapped.
- Use the similarity percentage as a first-pass signal, then review the actual added/removed lines for specifics.
- For code or structured content, keep formatting consistent between versions so the diff reflects meaningful changes only.
Tips
- If you need word-level precision, narrow the comparison to a single paragraph or sentence at a time rather than a whole document.
- Check the similarity percentage first — a very low score usually means the two texts are fundamentally different rather than lightly edited.