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Text Diff Checker

Compare two blocks of text and highlight the differences.

Paste text on both sides to compare.

Key features
Line-by-line diff, similar to a git diff
Highlights the exact characters changed within an edited line
Updates live as you edit either side
Shows a quick summary of additions and deletions
100% private — compared locally, nothing is uploaded
Paste an original and a modified version of some text to see a line-by-line diff — added lines, removed lines, and unchanged lines are clearly marked, similar to a git diff.


Everything is compared locally in your browser. Neither block of text is uploaded or stored anywhere.


How to use
  1. Paste the original text
    The starting version, on the left.
  2. Paste the modified text
    The updated version, on the right.
  3. Read the diff
    Added, removed, and unchanged lines are highlighted below.
Frequently asked questions
How does the comparison work?
It compares text line by line using a longest-common-subsequence algorithm — the same underlying approach most diff tools use — to find the smallest set of added and removed lines that explains the difference between the two versions.
Does it compare word by word within a line?
Lines are matched up first, same as a normal line diff. When a line on one side has a matching edited line on the other, the two are compared character by character and only the parts that actually changed are highlighted — so fixing a typo highlights just that typo, not the whole line.
Is there a size limit?
Very large inputs (several thousand lines on each side) may be slow to compare in the browser, since the algorithm’s cost grows with the size of both texts multiplied together.
Is my text uploaded anywhere?
No. Both blocks of text are compared entirely in your browser — nothing is sent anywhere.
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