How to use it
- 1Paste the original text into the first box and the changed text into the second.
- 2The comparison appears straight away: added lines are green, removed lines red, and the changed words inside a line are highlighted.
- 3Compare by lines, words or characters, and switch between the side-by-side and unified views.
- 4Turn on “Ignore whitespace” or “Ignore case” to skip differences that don’t matter, such as extra spaces or capital letters.
How the comparison works
The checker looks for the smallest set of changes that turns the original into the changed text, using the Myers diff algorithm – the same approach git diff uses. A line that exists only in the original is shown as removed, a line that exists only in the new version as added, and inside a modified line the words that changed are highlighted.
Comparing by lines suits code, lists and configuration files. Comparing by words works best for prose, where a single edit can reflow a whole paragraph. Comparing by characters shows every changed letter, which helps with names, codes and IDs. Long unchanged stretches are folded away so the changes stand out – click one to expand it.
Checking whether two values match
Comparing two long strings by eye – API keys, checksums, serial numbers, bank account numbers – is slow and error-prone. Paste one into each box: when they match, you’ll see “The texts are identical”; when they don’t, the characters that differ are highlighted.
Invisible differences show up too, such as a trailing space, a tab instead of spaces or an extra empty line at the end. With “Ignore whitespace” or “Ignore case” turned on, the checker tells you when two texts differ only in those details.
Questions and answers
Is it safe to paste confidential text?
Yes. The comparison runs entirely in your browser, and neither text is uploaded or stored. That makes it suitable for contracts, source code or configuration files with passwords in them.
What does “Ignore whitespace” do?
Lines that differ only in spaces or tabs – indentation, trailing spaces or several spaces in a row – count as equal, and empty lines are skipped. It’s useful when code has been reformatted or text was copied from a document with different spacing.
What is the difference between side-by-side and unified view?
Side by side shows the original on the left and the changed text on the right, with matching lines aligned – easy to read on a wide screen. Unified view lists everything in one column, with removed lines marked − and added lines marked +, like git diff. It works better on phones.
Can I compare two files?
Yes – open both files in a text editor, copy their contents and paste them here. It works well for code, CSV, JSON, configuration files and logs, even with tens of thousands of lines. For Word documents or PDFs, copy the text out of them first.
Why are lines I didn’t change marked as changed?
Usually because of characters you can’t see: trailing spaces, tabs instead of spaces, or non-breaking spaces copied from a web page or word processor. Turn on “Ignore whitespace”, or compare by characters to see exactly which characters differ.