Free Text Diff Checker
Compare two blocks of text and instantly see what changed, line-by-line or word-by-word, with a similarity score — right in your browser.
Compare textNo signup. No server calls. Works offline once the page loads.
Paste text on both sides to see a comparison.
How It Works
Paste both versions
Put the original text on the left and the changed version on the right.
Choose a comparison mode
Compare whole lines for documents and code, or individual words to spot small edits within a sentence.
Review the highlighted result
Additions and deletions are color-coded, with counts and a similarity score summarizing the change.
Privacy note: the comparison runs entirely in your browser using JavaScript. Neither text is sent to a server.
Common Uses
Reviewing document edits
See exactly what changed between two drafts of an essay, contract, or article.
Comparing code snippets
Spot line-level changes between two versions of a function or config file.
Checking translation or copy edits
Use word mode to catch small wording changes between two versions of a sentence.
Auditing plagiarism or paraphrasing
Use the similarity score to gauge how closely two passages match.
Frequently Asked Questions
How does the diff algorithm work?
The tool finds the longest common subsequence between your two texts, the same core principle used by the Unix diff command and Git. Everything in that shared subsequence is marked unchanged, and everything else is marked as either removed from the original or added in the changed version.
What is the difference between line mode and word mode?
Line mode compares whole lines against each other, which is best for comparing paragraphs, code, or documents. Word mode compares individual words within a line, which is best for spotting small edits inside a single sentence or short passage.
What does the similarity percentage mean?
Similarity is calculated as twice the number of matching lines or words divided by the combined length of both texts, expressed as a percentage. 100% means the texts are identical, and 0% means they share nothing in common.
Can I ignore capitalization differences?
Yes. Turning on "Ignore case" compares text without regard to uppercase or lowercase letters, while still displaying your original text exactly as typed.
Is there a limit to how much text I can compare?
The line-by-line and word-by-word comparison runs entirely in your browser, so very large inputs can be slow. The tool shows a message instead of freezing if a comparison would be too large to compute quickly.
Is my text uploaded anywhere?
No. Both texts are compared locally in your browser using JavaScript. Nothing you type is transmitted to a server, logged, or stored.