Diff Checker: how to use it (and read the results)

What this tool does

The Diff Checker compares two blocks of text and highlights exactly what changed: lines that were removed are marked in red, lines that were added are marked in green, and unchanged lines are left plain. It compares line by line using a longest-common-subsequence algorithm — the same idea behind git diff — and runs entirely in your browser.

How to use it

1. Open the Diff Checker.
2. Paste the original text on the left and the changed text on the right (or press Load sample to see an example).
3. Click Compare.
4. Switch between Side-by-side and Inline to view the result the way that suits you.

Reading the result

• Side-by-side puts the original on the left and the changed version on the right, aligned line for line. Removed lines are highlighted on the left; added lines on the right.
• Inline merges both into a single column. Removed lines start with - and added lines with +, like a unified diff.
• The status line summarises the change as a count of lines added and removed.

Why a diff checker is useful

• Spotting what changed between two drafts of an article or contract.
• Reviewing edits to a config file or block of code before applying them.
• Checking that text copied between tools wasn't altered.
• Comparing two error messages or log snippets that look almost the same.

Your text stays private

Both versions are compared locally in your browser — nothing is uploaded. That makes the tool safe for confidential drafts, internal code, and sensitive documents.

FAQ

Is my text uploaded anywhere?

No. The comparison happens entirely in your browser; nothing leaves the page.

Side-by-side vs inline — which should I use?

Side-by-side is best for reading two full versions at once; inline is best for scanning a compact list of just the changes.

Does it diff by line or by word?

By line — whole lines are marked added or removed, which keeps most reviews clear.

Ready to try it? Open the Diff Checker →