Text Diff Checker
Frequently Asked Questions
How text comparison works
How does text comparison work?
The tool uses the LCS (Longest Common Subsequence) algorithm to compare the two texts line by line. Green lines are those present in the right text but not the left (added), red lines are present only in the left text (removed), grey ones are identical in both.
Is the comparison case-sensitive?
Yes, the comparison is case-sensitive by default: "Hello" and "hello" are considered different lines. For a case-insensitive comparison, convert both texts to lowercase before pasting.
How many lines can I compare?
The tool works entirely in the browser and has no technical limits imposed server-side. However, for very long texts (over 10,000 lines) the LCS algorithm may slow down due to O(m×n) complexity. For large files, consider using command-line tools like diff or git diff.
Is my data sent to a server?
No. All comparison happens directly in your browser via JavaScript. No data is sent to external servers. You can safely use this tool even with texts containing confidential information.
How are two texts compared line by line?
To compare two texts you paste the original into one box and the edited version into the other. The result shows the added lines, the removed ones and the ones left unchanged straight away.
Are the texts sent to a server?
No. The comparison between the two texts happens inside the browser, so the original and the edited version stay in the page and are not sent anywhere to be processed.
What do the colors in the result mean?
Lines in green with a plus sign are only in the edited text, lines in red with a minus sign belong only to the original, and the rest are unchanged.