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Diff Checker

Paste two versions and see exactly what was added, removed, and changed.

Compare two texts

Never uploaded

Your file is processed in this tab and never sent anywhere.

The ads come from Google. Your files stay on your device.

How to compare two texts

  1. Paste the original. Into the left box, or drop a text file on it.
  2. Paste the new version. Into the right box.
  3. Read the differences. Additions, removals, and changes are marked line by line.

About Diff Checker

Comparing two versions of something by eye is a task humans are reliably bad at. Move a paragraph, change a number in the middle of a page, or alter one clause in a contract and it can be read three times without anyone spotting it. A diff does this mechanically, and the result is that the change either appears or it does not: there is no attention budget involved.

The comparison here works line by line using a longest-common-subsequence approach, which is the same family of algorithm that powers version control diffs. It finds the largest set of lines the two versions share in order, and everything outside that set is marked as added or removed. Changed lines show up as a removal paired with an addition, since a line is either identical or it is not.

The common uses are contracts, configuration, and code. A revised agreement returned by the other side needs checking against what you sent, and the change is rarely announced. A config file that used to work needs comparing against the one that does not. Two versions of a script have drifted and it is not obvious how. In each case the diff answers the question in seconds.

That first case is exactly why this runs locally. Comparing two drafts of a contract on a website means pasting both drafts into someone else's server, which is a strange thing to do with a document you are negotiating. Everything here happens in the browser tab: the text is never transmitted, and you can confirm that in the Network panel of your developer tools.

Diff Checker FAQ

Is my text uploaded when I compare it?

No. The comparison runs in this browser tab. Nothing is transmitted, which matters when the two things you are comparing are drafts of a contract.

Can I compare two files rather than pasting?

Yes. Drop a text file onto either box and its contents load in. Plain text, code, CSV, and similar formats all work.

Does it compare word by word or line by line?

Line by line. A changed line appears as a removal and an addition together, since a line either matches exactly or it does not.

Can I compare two PDFs or Word documents?

Not directly. Convert them to text first with PDF to Text or by copying the content, then paste the results here.

Is there a size limit?

No fixed limit, though very large inputs will slow the browser down since the comparison happens on your device.

Does it ignore whitespace?

There is an option for that. Turn it on when indentation has changed but the content has not.

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