Text Difference Checker
Paste two versions of text and see a line-by-line diff of what was added, removed or unchanged — computed locally.
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What is the Text Difference Checker?
This checker compares two blocks of text and highlights added, removed and unchanged lines using a longest-common-subsequence diff.
How to use it
- 1Paste the original text on the left.
- 2Paste the changed text on the right.
- 3Read the highlighted diff.
How it works
The two inputs are split into lines and compared with a longest-common-subsequence algorithm, which produces the minimal set of insertions and deletions.
Limitations & notes
- The optional word mode compares tokens; it does not show character-level edits inside a word.
Frequently asked questions
Why does every line show as changed when the text looks identical?
Invisible differences are counted. The most common is line endings: a file saved on Windows ends lines with CRLF, so each line carries an extra carriage return that a Unix copy lacks. Trailing spaces, tabs versus spaces, and non-breaking spaces cause the same result. Normalize both versions first, for example by trimming whitespace in a cleanup tool, and compare again.
When should I use word comparison instead of line comparison?
Line comparison suits code, configuration files and lists, where each line is a unit. Word comparison suits prose, where one edited word would otherwise mark a whole paragraph as removed and re-added. In word mode, inserted words are highlighted and deleted words are struck through inline. A typo fixed inside a word still shows the entire word as replaced, since characters are not compared individually.
How does the diff handle a paragraph that was moved?
A longest-common-subsequence diff has no concept of a move. If you cut a block from the top and paste it at the bottom, it appears as removed in one place and added in another, and the counters include both. Unchanged lines between them stay aligned. Comparing sorted copies of the two texts is a quick way to check whether content only moved.
Is the comparison case-sensitive, and can I export the result?
Yes, it is case-sensitive: Hello and hello count as different. Copy diff produces plain text where each line starts with + for added, - for removed or a space for unchanged, similar to the unified format used by git, which is easy to paste into a ticket or chat. Swap sides reverses which text counts as the original.
How much text can I compare?
Each side can hold up to 30,000 characters, roughly 5,000 words or several hundred lines of code. Beyond that the tool shows a warning instead of a diff, because the comparison table grows with the product of both lengths and could freeze the tab. For larger files, compare section by section or use a command such as git diff --no-index on your machine.
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