How to use the Diff Checker: Compare Two Texts
- Paste the original on the left and the new version on the right, or use Open file or drag a file onto each box.
- The differences appear below as you type. Press Ctrl+Enter or click Compare any time.
- Switch between Side by side and Unified views. Tick Only show changes to hide matching sections in long files.
- Use Ignore whitespace or Ignore case to skip changes that don't matter, and Download .diff to save a standard patch.
How the comparison works
The checker uses the Myers diff algorithm, the same approach used by Git, to find the smallest set of line additions and removals that turns the original into the new text. Lines that were edited are then compared word by word, so a single changed number or word stands out instead of the whole line.
What people compare
- Code and config files: spot the change that broke a build, or review edits before you commit.
- JSON and API responses: format both with the JSON formatter first, then compare to see which fields changed.
- Contracts and documents: check what the other side changed in a revised draft.
- Lists and spreadsheets: paste two columns to find items that were added or removed.
Side by side or unified?
Side by side shows the original and the changed version next to each other, which is easiest to read. Unified shows one column with - for removed and + for added lines, the format used by Git and code reviews. Download .diff saves a standard unified patch that tools like git apply and patch understand.
Frequently asked questions
Is it safe to compare confidential text?
Yes. The comparison runs entirely in your browser. Your text is never uploaded or stored.
How large can the files be?
Files up to 10 MB each. Very different texts (more than 3,000 changed lines) are too slow to compare line by line in a browser.
Can I ignore spaces and indentation?
Yes. Tick <b>Ignore whitespace</b> to treat lines as equal when they differ only in spaces, tabs or indentation.
Can I compare Word or PDF files?
The checker compares plain text. Copy the text out of the document and paste it into each box.
What do the colors mean?
Red is removed from the original, green is added in the changed version. Darker highlights mark the exact words that changed inside a line.