How Text Diff Checker Works
The tool compares the two texts line by line using a longest-common-subsequence algorithm — the same underlying approach version control tools use — to find the smallest set of additions and removals that turns the original into the changed version. Lines are shown unchanged, or marked as removed (from the original) or added (in the changed version).
How to Use This Tool
- Paste the original text on the left and the changed text on the right.
- Select Compare.
- Removed lines are shown struck through in red, added lines in green, and unchanged lines in the normal color.
Example
Comparing Hello world
Goodbye with Hello there
Goodbye shows Hello world as removed, Hello there as added, and Goodbye as unchanged.
Helpful Tips
- This compares whole lines, not individual words — a single changed word will show its entire line as removed and re-added.
- Trailing whitespace differences count as a change — trim both texts first if you only care about content, not formatting.
Frequently Asked Questions
Does this compare word-by-word or line-by-line?
Line by line. If you need to spot a single changed word within a long line, look closely at the removed/added pair for that line.
Is my text uploaded anywhere?
No, the comparison runs entirely in your browser.
Can I compare code with this?
Yes, line-based diffing works well for code, configuration files, or any other line-structured text.
This tool runs entirely in your browser. Your input is not uploaded to any server.