What is a diff checker?

A diff checker compares two versions of a text and shows what is different between them: lines that were removed, lines that were added and the words that changed inside a line. It is useful for proofreading edits, reviewing changes to a contract, comparing code or finding what changed in a config file.

How do I compare two texts?

Paste the original version in the left box and the new version in the right box, then select Find differences. Removed text is marked in red and added text in green. You can also press Ctrl + Enter, or Cmd + Enter on a Mac, from either box.

Is my text uploaded or stored?

Not unless you save it. The comparison runs entirely in your browser. If you select Save and share, both texts are stored so the link can show the comparison to anyone who opens it.

How do I share a comparison?

Compare the two texts, then select Save and share. You get a read-only link that shows the same differences. Saved comparisons cannot be changed, but anyone who opens the link can edit the texts below the result and save them under a new link.

Can I compare code, JSON or CSV files?

Yes. The diff checker works with any plain text, including source code, JSON, YAML, CSV and logs. Spacing is kept exactly as you pasted it.

Is there a size limit?

Comparing has no fixed limit, but very long texts that are almost completely different can take too long to compare in a browser. If that happens you will see a message, and comparing smaller parts works best. To save and share a comparison, each text can be up to 1,000,000 characters.

Online diff checker

Compare two texts and see every change, line by line.

Split

Unified

Real-time editor

Hide unchanged lines

Disable line wrap

Ignore whitespace

Ignore case

Go to first change

Texts edited. Compare again to update.

The two texts are identical.

These texts are too different to compare in your browser.

Try comparing smaller parts of the text at a time.

Swap texts

See exactly what changed between two texts

Fast Note's diff checker compares two versions of a text line by line. Paste the original on the left and the new version on the right, and every removed, added and changed line is highlighted, down to the words that differ. There is no account to create, and nothing is uploaded unless you save the comparison to share it.

Side by side or unified view

See the original and the changed text next to each other, or switch to a single column with removed and added lines one after the other. The single column works best on small screens.

Word level highlights

Inside each changed line, the exact words that differ are highlighted, so a fixed typo or a changed number stands out right away.

Ignore whitespace and case

Skip differences in spacing, indentation or capitalization when they do not matter, and focus on the changes that do.

Runs in your browser

The comparison happens on your device. Your text is only sent to Fast Note if you choose to save the comparison, so you can safely compare drafts, contracts and config files.

Long texts stay readable

Turn on Hide unchanged lines to fold the stretches that did not change, or use Go to first change to jump straight to the first difference. Open a text file instead of pasting it.

Share a comparison

Save the result to get a short, read-only link. Whoever opens it sees the same highlighted differences, with no account needed on either side.

Need to share one of the versions? Paste it into the online notepad or the plain text editor and get a link.

Your notes

Saved diffs