How to use Diff checker
- 1
Paste the original version on the left and the changed version on the right, or press "Load an example".
- 2
Read the summary of changed, added and removed lines. The comparison updates as you type.
- 3
Switch between side-by-side and unified views, and choose word or character highlights.
- 4
Tick "Ignore whitespace" or "Ignore case" to hide differences that don't matter to you.
- 5
Copy or download the unified patch to share the change or apply it with git apply.
What this tool does
The diff checker compares two texts line by line with the Myers diff algorithm, the same approach used by Git. Lines that only exist in the original are shown as removed, lines that only exist in the new version as added, and lines that were edited in place as changed, with the exact words or characters that differ highlighted inside them.
It works for any plain text: source code, configuration files, CSV exports, legal clauses or two drafts of an article.
Features
- Side-by-side or unified view, with line numbers for both versions.
- Word or character highlights inside changed lines.
- Ignore whitespace and ignore case options.
- Counts of changed, added and removed lines, plus warnings when line endings or the final line break differ.
- Collapse unchanged lines to focus on the changes, keeping three lines of context around each one.
- Swap sides in one click.
- Copy or download a unified patch (.patch) that works with git apply and patch.
Limits
- Plain text only. Word documents, PDFs and images aren't compared; copy their text in first.
- Lines are paired in order inside each changed block, so a moved paragraph shows as removed in one place and added in another.
- Lines longer than 4,000 characters are highlighted as a whole rather than word by word.
- Long results show the first 2,000 rows until you choose to show all.
Where your text is processed
This tool works in your browser: what you type or paste is processed on your own device, so it isn't sent to our server for this tool. Some other tools on UtiloNest do use our server, and their pages say so.
Frequently asked questions
Where is my text processed?
In your browser. This tool works on your own device, so what you type isn't sent to our server for it.
What does "Ignore whitespace" treat as equal?
Lines that differ only in the amount of spacing, such as indentation with tabs instead of spaces, trailing spaces, or two spaces between words instead of one. Removing a space completely, as in "a b" versus "ab", still counts as a change.
Why does it say my texts differ only in line endings?
Windows files usually end lines with CRLF and macOS or Linux files with LF. The checker treats both as the same line break, so a file isn't marked as changed on every line. It tells you when the line endings differ so you know the files aren't byte-for-byte identical.
What is the unified patch?
It's the standard diff -u format used by Git and the patch command, with --- and +++ headers and @@ hunks with three lines of context. It always contains every difference, even ones hidden by the ignore options, so applying it turns the original text into the changed one.
How large can the texts be?
There's no fixed limit. The comparison runs in a background worker, so the page stays responsive while you type, and identical starts and ends of the texts are skipped quickly. Very large texts that are almost completely different can hit a ten-second limit; the tool then says so instead of freezing.