How to use the Diff Checker tool
- Paste the original text on the left and the new version on the right.
- Click “Compare”. Tick the options to ignore whitespace or case.
- Review the highlighted lines, or copy everything as a unified diff (patch).
How the comparison works
The checker uses the Myers diff algorithm, the same one Git uses by default. It finds the smallest set of line insertions and deletions that turns the first text into the second. Lines that were changed are shown as a removal followed by an addition, and the words that differ inside them are highlighted, so a changed port number in a long config line stands out immediately.
Where it saves time
- Comparing a working and a broken config (nginx, Apache, sshd_config, Cisco running-config).
- Checking what a vendor changed between two versions of a contract or policy.
- Reviewing environment differences between staging and production .env files (never paste real secrets into any website you do not control).
- Turning a quick edit into a patch with the unified diff export.
Privacy
Everything runs in your browser. Nothing you type is sent to our server or stored.
Frequently asked questions
Does it compare words or lines?
Lines first, then words inside each changed line.
What does “Ignore whitespace” do?
It treats runs of spaces and tabs as one space and ignores leading and trailing spaces, which hides indentation-only changes.
Can I compare files?
Open the files in any text editor and paste their contents. Very large files (tens of thousands of changed lines) may be too slow in the browser.
Can I use the patch output with Git?
Yes, it is a standard unified diff, though without file names: add them to the --- and +++ lines before applying it with git apply or patch.