Text Diff Checker

What is it and how does it work

How to compare two texts

1. Paste the original text into box A and the changed text into box B.
2. The comparison updates instantly, marking each line as added, removed, or unchanged.
3. Check the summary counts for a quick overview of how much changed.

Use cases

When a diff checker is useful

Comparing two versions of a document, contract, or article by eye is slow and easy to get wrong once more than a few lines have changed. A diff checker is the same idea used by version-control systems like Git — it lines up matching content and highlights exactly what was inserted or deleted, making it easy to review edits, track changes between drafts, or confirm that only the intended lines were modified.

As a general-purpose text comparison tool, it works just as well for spotting the differences between two contract drafts, two essay revisions, or any pair of text files where you need to find what changed without reading both copies line by line.

Most frequently asked questions

FAQ

Is this text diff checker really free, with no sign-up?+

Yes. The tool runs entirely with JavaScript in your browser — there's no account, no API key, and no limit on how often you can use it.

Does my text get uploaded anywhere?+

No. Both texts are compared locally on your device. Nothing is sent to a server, stored, or logged.

How does the comparison work?+

The tool compares the two texts line by line using a longest-common-subsequence algorithm, the same general approach used by most version-control diff tools, and marks each line as added, removed, or unchanged.

Does it compare individual words, or whole lines?+

This checker compares at the line level. If a line has even a small change, the whole line is marked as changed rather than highlighting the specific word that differs.

Is the comparison case-sensitive?+

Yes, by default two lines that differ only in capitalization are treated as different lines.

Related tools

Tools for Text Analysis

• Word Frequency Counter — see how many times each word appears in a text, ranked by frequency.
• Duplicate Line Remover — strip out repeated lines from any list or block of text.
• Hash Generator — generate SHA-1, SHA-256, SHA-384 and SHA-512 hashes from text.

Methodology

How This Checker Works

Your two texts are compared live with JavaScript using a longest-common-subsequence algorithm, the same general approach used by most version-control diff tools — nothing you paste is uploaded to a server or stored anywhere.

Last updated: August 28, 2026.