Text Diff Checker
Paste an original text and a changed text to see exactly what differs. The comparison uses a longest common subsequence so it keeps the largest run of matching lines and marks everything else as added or removed. Switch between line, word and character modes, side by side or unified views, and count the additions and removals at a glance.
How to compare two texts
- Paste the original into the Original box on the left, or drop a text file onto it.
- Paste the new version into the Changed box on the right.
- Pick a Mode of Line, Word or Character to control how finely changes are highlighted.
- In line mode, choose Side by side or Unified, and tick Collapse unchanged to hide long matching sections.
- Optionally enable Ignore whitespace or Ignore case to skip trivial differences.
- Read the plus, minus and modified counts, then use Copy .diff or Download .diff to export.
Examples
One line edited
line one / line two / line three vs line one / line 2 / line three
line one and line three unchanged, line two shown changed to line 2
Identical text reports no changes
same paragraph pasted into both boxes
No differences. The two texts are identical.
Only casing differs with Ignore case on
'Hello World' vs 'hello world', Ignore case ticked
No differences under the current options
Frequently asked questions
How does the diff decide what changed?
It computes the longest common subsequence of lines, the longest run that appears in both texts in the same order. Lines inside that run are unchanged, and anything outside it is marked as added on the right or removed on the left. This keeps genuine edits visible without flagging matching lines.
What do line, word and character modes do?
Line mode compares whole lines and offers side by side or unified views. Word and character modes run a finer diff across the text and highlight the exact words or characters that differ inline, which is useful for spotting a single changed word in a long sentence.
Why does an edited line sometimes split into a remove plus an add?
A line level diff has no partial match for a changed line, so in unified view the old line appears with a minus and the new line with a plus. In side by side line mode the two are aligned as a modified pair with the changed part highlighted inline.
What do Ignore whitespace and Ignore case do?
Ignore whitespace treats lines that differ only in spaces, tabs or indentation as equal. Ignore case treats letters as matching regardless of upper or lower case. With either on, texts that match apart from those details report no differences under the current options.
Does it handle Windows and Mac line endings?
Yes. CRLF, lone CR and LF endings are all normalized to a single newline before comparison, so the same content saved on different operating systems is not reported as different.
Can I export the result?
Yes. Copy .diff puts a standard unified diff on your clipboard, and Download .diff saves it as a changes.diff file. The download button is enabled only when there are actual differences to export.
Is there a size limit for word and character modes?
The finer word and character diffs are capped for responsiveness. When the two texts multiplied together grow very large, the tool asks you to switch to Line mode, which stays fast on big inputs.
Can it detect reordered or moved lines?
It preserves the longest in-order match, so a block that moved shows as a removal where it used to be and an addition where it now sits. It does not draw a link between the two positions, since the diff works on order rather than tracking moves.
Is my text uploaded anywhere?
No. The comparison runs entirely in your browser and nothing you paste is sent to a server. Using the optional Share this comparison link is the only action that stores the two texts, and only when you choose it.
Learn more
- Line, word and character diffs, and when to use each
How line, word and character comparison differ, why an edit can show as a remove plus an add, and which mode fits prose versus code.
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