Diff Checker
Paste two blocks of text and instantly see every addition, deletion, and change highlighted line by line. Perfect for code reviews, config files, and document comparisons. Free, private, runs in your browser.
How to compare two texts
Paste two versions, compare them, and see every added and removed line.
- 01
Paste the original on the left and the new version on the right
Code, contract clauses, config files, essays: any plain text works. Sample loads two versions of a small function to show the output.
- 02
Compare
Unchanged lines stay plain, lines only on the left are marked as removed, and lines only on the right as added. Each side keeps its own line numbers.
- 03
Copy or download the result
The export puts + in front of added lines and − in front of removed ones, which is easy to paste into a review comment or an email.
How the comparison finds changes
The tool splits both texts into lines and finds their longest common subsequence: the largest set of lines that appear in both, in the same order. Those are shown as unchanged. Everything else is a removal from the left or an addition on the right. It's the same idea behind diff and Git's line-based view.
Lines must match exactly, character for character. Change one word in a sentence and the whole line is reported as removed and re-added. Here's a short letter where only "quick" was added:
| Result | Line |
|---|---|
| Unchanged | Dear Priya, |
| Removed | Thanks for the update. |
| Added | Thanks for the quick update. |
| Unchanged | The invoice total is ₹12,400. |
| Unchanged | Regards, |
There's no highlighting inside a line, so for prose it helps to put each sentence on its own line before comparing. The changed sentence is then easy to spot, and the rest of the paragraph stays marked as unchanged.
Getting a clean diff
Invisible differences cause most noisy results. A file saved on Windows has \r\n line endings, one from macOS or Linux has \n, and trailing spaces or a tab instead of spaces make otherwise identical lines differ. If every line shows as changed, that's the likely cause. Normalise line endings in your editor, or paste both sides from the same place.
Reformatting is the other trap. If one version was run through a code formatter or re-wrapped at a different line width, almost every line changes even though the meaning didn't. Format both versions the same way first, then compare.
When a text diff helps
Checking edits to a contract
Compare the draft you sent with the one that came back to find every clause the other side changed.
Reviewing a config change
Paste the old and new versions of a .env, YAML or nginx file to see exactly which settings moved.
Spotting what an AI rewrite changed
Put the original paragraph and the rewritten one side by side, one sentence per line, to judge each change.
Limits worth knowing
- It compares whole lines only, with no word or character highlighting.
- Comparisons need memory for every pair of lines, so each side should stay under about 5,000 lines. Larger inputs are refused with a message rather than freezing the tab.
- There's no ignore-whitespace or ignore-case option. Clean those differences up before comparing.
- The exported text uses a − sign for removed lines and isn't a patch file. For something you can apply, use git diff or diff -u.