Text Diff Checker — Free Online Tool

🔍 Text Diff Checker

Spotting the differences between two versions of a document, a paragraph, or a block of code by eye is slow and error-prone once the text gets longer than a couple of lines. This diff checker compares two blocks of text line by line and highlights exactly what was added and what was removed, so changes jump out immediately.

It's useful for reviewing edits to an article, comparing two versions of a config or code snippet, or checking what changed between two drafts of a document — all processed locally in your browser.

How to use the Text Diff Checker

Paste the original text into the first box.
Paste the changed/new text into the second box.
Click compare to see a line-by-line diff, with additions and deletions highlighted.

How the comparison works

The tool splits both texts into lines and computes the longest common subsequence (LCS) of matching lines between the two versions — a standard diff algorithm also used by tools like diff and version control systems. Lines present only in the second text are marked as additions, lines present only in the first text are marked as deletions, and unchanged lines are shown as-is.

Frequently asked questions

Is the comparison case-sensitive?

Yes, by default the comparison treats differently-cased text as different — 'Hello' and 'hello' will be flagged as changed. This mirrors how most code and document diff tools behave, since case often matters.

Can I compare paragraphs of prose, not just code?

Yes — the diff works line by line on any plain text, whether it's prose, code, CSV data or configuration files. For best results with prose, keep sentences on separate lines where possible so changes are easier to isolate.

Is my text uploaded anywhere?

No, the comparison runs entirely in your browser using JavaScript. Neither text box's content is sent to a server, which makes it safe to use for private or confidential documents.