Diff Checker
Compare two blocks of text or code and highlight differences
What is this tool?
Compares two blocks of text or code and highlights exactly what's different between them, line by line.
How to use it
Paste your two versions of the text into the two panels, and the differences are highlighted automatically.
This is useful well beyond code — comparing two drafts of a document, or two versions of a contract, works the same way and is often faster than manually reading both side by side.
Watch: Diff Checker in Action
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Frequently asked questions
How to use Diff Checker
Paste your first version of the text or code into the left panel and your second version into the right panel. The differences are highlighted automatically, line by line -- added lines, removed lines, and changed lines are each marked distinctly so you can quickly scan for exactly what changed between the two versions without manually reading through both side by side looking for differences yourself.
When to use it
The most direct use is comparing two versions of code -- checking exactly what changed between a working version and a new edit before committing, or reviewing someone else's proposed change line by line. It's equally useful well beyond code: comparing two drafts of a document or contract to see exactly what was edited, checking a revised email against the original before resending, or verifying that a "find and replace" operation in a large document only changed what you intended it to.
When not to use it
For comparing entire files or folders with many files at once (a real codebase's full set of changed files across a whole commit, for instance), a version-control system's own diff view or a dedicated file-comparison tool built for that scale is more practical than pasting file contents in one pair at a time. If what you actually need is to merge two versions together (combining changes from both rather than just seeing what differs), that's a related but different operation -- a merge tool, not a diff viewer, is built for that.
Tips for best results
For comparing longer documents, it can help to paste in smaller, focused sections rather than an entire long document at once -- a shorter comparison is faster to visually scan for the specific differences you're actually looking for, especially if most of the document is unchanged and only a small section is genuinely different.
Limitations
Comparison is line-by-line text matching -- it doesn't understand the semantic meaning of code or prose, so a change that reorders content without altering its meaning (moving a paragraph, or reordering function arguments in a way that doesn't change behavior) will show as a difference even though the practical result may be equivalent.
Privacy
Both texts are compared entirely in your browser -- neither version of your text or code is uploaded to any server, which matters in particular for comparing code or documents you wouldn't want leaving your device.
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