Diff Checker
Compare two blocks of text side-by-side or inline. Highlights additions, removals, and changes. Runs in your browser.
Runs entirely in your browser. Nothing is sent to our servers.
About this tool
Paste two blocks of text and see what's changed between them — line by line.
The comparison uses the Myers diff algorithm (the same one underlying
git diff) to find the shortest list of changes. Results are
computed in your browser; nothing is uploaded.
Reading the output
In side-by-side mode, the left column is the original and the right column
is the changed version. Removed lines are tinted red on the left; added
lines are tinted green on the right; modified lines appear opposite each
other in both colours. Inline mode shows a unified diff in
+/- style, ready to paste into a pull request or a patch file.
Frequently asked questions
- Does this handle binary files?
- No — it expects text. If you paste binary content, you'll see one giant "line" because there are no newlines to split on. Use
diffon the command line for binary comparisons. - Can I download the diff?
- Use the inline (unified) view, select all, and copy. The format is a valid unified diff that
git applyandpatchunderstand, once you add a properdiffheader. - Why are some lines marked as changed when only whitespace differs?
- Whitespace within a line matters for the diff — the algorithm sees character-level differences. Enable "Ignore trailing whitespace" to skip differences at line ends. Differences in leading whitespace are still shown because they often indicate real meaning (indentation, scope).
- How big can the inputs be?
- A few thousand lines on each side runs in a fraction of a second. For very large files (tens of thousands of lines), the algorithm slows quadratically — use
git diffor a desktop tool instead.
Last updated: May 17, 2026