Diff Checker
Compare two blocks of text, line by line.
Paste two versions to compare
Added lines are highlighted in green; removed lines are struck through in red.
Common questions
Is my text uploaded anywhere?
No. The comparison runs entirely in your browser, so both blocks of text stay on your device.
How does the comparison work?
It compares the two inputs line by line and marks each line as unchanged, added, or removed, using a longest-common-subsequence match so unrelated lines are not paired by mistake.
What do the colors mean?
Added lines are highlighted in blue; removed lines are red with a strikethrough. The bar on the right maps every change to its place in the file so you can see where edits cluster.
Does it handle large files?
Yes. Long lines wrap instead of scrolling sideways, and the change overview keeps a single changed line visible even among thousands.
Does it compare word by word?
The diff works at the line level. To spot a small change inside a long line, split it across lines first.