Text Diff Checker
Compare two versions and see exactly what changed. Free, local and private—no account needed.
Compare in this tab. No text is sent or saved. Spaces and line breaks count as changes. Each field accepts up to 20,000 UTF-16 units: most characters use one, an astral emoji uses two. Long pastes are never cut. One side may be empty.
Enter text on either side to compare. One side may be empty.
How the comparison works
The checker compares words, punctuation and whitespace without changing either input. Added, Removed and Modified count separate change blocks, not words. Adjacent additions and removals form one Modified block; unchanged text separates blocks.
Calculation has a 100 ms time budget and a 1,000-edit work limit. If either is exceeded, no partial result is shown. Your texts stay intact so you can compare shorter passages. Editing either input clears the previous result.
A comparison, block by block
A short note before and after an edit, marked the way this checker marks it: green is added, red and struck through is removed, amber is modified on both sides. The counts are the ones the tool reports for this pair.
- Added
- 2
- Removed
- 1
- Modified
- 1
The launch is on Monday. Please review the draft carefully and send comments to Sam.
The launch is on Thursday, May 5. Please review the draft and send your comments to Sam by Wednesday.
Modified: Monday → Thursday, May 5
One Modified block, not a removal and three additions: the old word and the new words sit in the same place with no unchanged text between them, so the replacement counts once.
Removed:
carefullyNothing takes its place. The word and the space after it go together, because both disappear between the same unchanged neighbours.
Added: your
New text with unchanged text on both sides, so it forms a block of its own.
Added: by Wednesday
Two words and their spaces make one block, because nothing unchanged separates them.
What counts as a change
The comparison ignores nothing. Capital letters, punctuation, accents, spaces and line breaks all count, so two versions that look alike can still differ. Each pair below shows the checker’s own result.
- Original
cat
- Modified
dog
- Original
keep
- Modified
keep tail
- Original
a
bc- Modified
a c
- Original
cat and dog
- Modified
bat and fox
- Original
Hello, world!
- Modified
hello, world?
- Original
café
- Modified
cafe
Some differences do not show on screen at all, and still count:
- A non-breaking space where the other version has an ordinary space: 1 modified block.
- A tab where the other version has a space: 1 modified block.
- Windows line breaks (CRLF) against Unix ones (LF): 1 modified block.
Frequently asked questions
What do the added, removed and modified counts mean?
The comparison groups adjacent changes into blocks. A block only in the newer text is added; one only in the original is removed. A block containing both removed and added text is modified. These are block counts, not numbers of edited words or characters.
How precise is the comparison, and what are its limits?
It compares words and punctuation while preserving whitespace, with both panes retaining the exact text supplied. Each input has a length limit, and the comparison has time and edit-size limits. A large or very different pair may be refused; the tool reports that instead of showing a partial comparison.
Does comparing text rewrite or merge either version?
No. It displays differences without editing, merging or judging the quality of either version. Both texts stay in your browser. You decide which changes to use, and following a link to the rewriter does not send either input there.
Related tools
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