Text Diff Checker
Compare two blocks of text and instantly see exactly what changed, line by line.
How to use the text diff checker
- Paste your original text into the left box.
- Paste the changed or updated version into the right box.
- Click Compare to run the line-by-line comparison.
- Removed lines appear in red with a "−" marker, added lines in green with a "+" marker, and unchanged lines appear plain.
Why use a text diff checker?
Spotting the difference between two versions of a document, article, or config file by eye is slow and error-prone, especially with long text. This tool runs a proper longest common subsequence (LCS) comparison — the same technique used by version control systems — to line up matching content and highlight exactly what was inserted or removed. It's useful for reviewing edited drafts, comparing contract revisions, checking changelog entries, or catching accidental changes in code snippets and configuration files. Everything runs locally in your browser, so sensitive text never leaves your device.
How does the diff checker compare two texts?
It uses a longest common subsequence (LCS) algorithm to find lines that appear in both texts, then marks everything else as either removed (only in the original) or added (only in the changed version).
Does it compare word-by-word or line-by-line?
This tool compares line by line, which is ideal for paragraphs, code, lists, and configuration files where each line represents one unit of content.
Is my text stored or uploaded when comparing?
No. The comparison runs entirely in your browser using JavaScript. Neither text box is ever sent to a server.