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Text Diff Checker

Find every difference between two versions of a document or code file. Switch between line, word and character comparison and view changes side by side or inline.

  • Runs in your browser
  • Free, no sign-up
  • No uploads

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What is a Text Diff Checker?

In software development and content creation, it is incredibly common to have two versions of the same document. Perhaps you have an original draft and a revised draft, or an old configuration file and a new one.

A Text Diff (Difference) Checker is a specialized tool that analyzes two blocks of text side-by-side and visually highlights every single insertion, deletion, and modification.

Instead of reading through 500 lines of code trying to find a single missing semicolon, a diff checker instantly colors the exact character that changed.

Common Use Cases

Diff checkers are essential tools for a variety of professionals:

  • Software Developers: Before committing code to a repository (like Git), developers use diff tools to review their changes and ensure they haven't accidentally broken surrounding logic.
  • System Administrators: When an application crashes, admins use diff checkers to compare the current server configuration file against a working backup to instantly spot what was changed.
  • Writers and Editors: Authors can compare their original manuscript against an editor's revised copy to see exactly which sentences were rewritten or deleted.
  • Legal Professionals: Lawyers use redline diffing to compare two versions of a highly complex contract to ensure no secret clauses were inserted during negotiations.

How the Algorithm Works

Modern diff checkers use complex string-matching algorithms (most famously the Myers diff algorithm) to find the Longest Common Subsequence between two files.

The tool attempts to find the largest chunks of text that match perfectly, and then works backward to identify the smallest possible edits (additions or subtractions) required to transform the original text into the new text.

Secure Client-Side Diffing

When comparing proprietary source code, confidential legal contracts, or unreleased manuscripts, privacy is paramount.

If you use a cloud-based diff tool, you are uploading both versions of your highly sensitive documents to a remote server. Our Text Diff Checker eliminates this risk entirely. The complex Myers algorithm runs natively inside your web browser using JavaScript. The comparison happens on your local CPU, ensuring your confidential documents never touch the internet.

How to use the Text Diff Checker

  1. 1

    Paste the original text on the left and the changed text on the right.

  2. 2

    Choose line, word or character comparison.

  3. 3

    Review highlighted additions and deletions, then copy a unified patch if needed.

Features

Three granularities
Compare by line, word or character.
Side-by-side or inline
Pick the view that suits your review.
Ignore options
Ignore case and whitespace changes.
Patch export
Copy a unified diff you can apply with git.

Frequently asked questions

Can I compare code files?

Yes. Drop files onto either panel. Line mode works best for code, while word mode is ideal for prose.

What algorithm is used?

The tool uses the Myers diff algorithm (via the jsdiff library), the same approach used by git.

Are my texts uploaded to a server?

No. All processing happens locally in your browser using JavaScript and WebAssembly. Your texts never leave your device, and nothing is stored or logged.