Text Diff Checker

This tool uses the Myers diff algorithm (developed by Eugene W. Myers in 1986), which is the industry standard for computing differences between texts. It's the same algorithm powering Git, Unix diff, and most modern version control systems. The Myers algorithm efficiently finds the shortest edit script (smallest set of changes) to transform one text into another, making it both fast and accurate even for large files.

The generated unified diff patch follows the standard format used by Git and Unix patch tools. You can apply it using: "git apply patch.diff" for Git repositories, "patch < patch.diff" for Unix patch command, or import it into version control systems. The patch includes headers showing old and new file names, line number ranges (@@), and all changes with +/- markers, making it a portable way to share or apply changes.

Ignoring whitespace is crucial when comparing code because formatting changes (indentation, spacing, line endings) don't affect functionality but can create hundreds of false "changes." This is especially important when: comparing code formatted by different editors or linters, reviewing changes after auto- formatting, working across different operating systems (Windows vs Unix line endings), or when team members use different tab/space settings. Ignoring whitespace lets you focus on actual code changes that matter.

Split view shows both texts side-by-side in parallel columns, making it easier to see context and structure of both versions simultaneously. It's better for understanding overall changes and seeing how modifications affect surrounding code. Unified view combines both texts into a single column with +/- markers, which is more compact and matches Git's output format. Use split view for detailed review and context, unified view for quick scanning or when familiar with Git patch format.

No, this tool is designed specifically for text file comparison. Binary files (images, executables, compressed files, PDFs) require specialized binary diff tools that work with bytes rather than text characters. For images, use visual diff tools that show pixel-by-pixel differences. For other binary files, consider tools like vbindiff or specialized diff utilities designed for binary data.

While the tool can handle reasonably large files (several megabytes), very large files may be slow to process or could crash your browser depending on your device's memory and performance. For best results, keep files under 1-2MB. For comparing very large files (10MB+), consider using command-line tools like diff, git diff, or specialized diff utilities designed for large-scale comparisons that don't run in the browser.

Use word-by-word comparison for prose, documentation, articles, or any natural language text where you want to see which specific words changed while maintaining readability. Use character-by-character for precise comparison needs: finding typos, comparing short strings, analyzing data values, or when you need to see exactly where individual characters differ. Line-by- line is best for code or structured text where line boundaries matter.

Yes, absolutely safe. All text comparison and diff computation happens entirely in your browser using JavaScript. No files or text content are ever uploaded to our servers, stored in databases, or transmitted over the internet. You can even disconnect from the internet after loading the page and the tool will continue to work offline. This makes it completely safe to compare sensitive documents, proprietary code, confidential contracts, or any private data.

You can either copy and paste text directly into the input areas, or use the file upload buttons to load text files from your computer. The tool supports any plain text file format (.txt, .js, .py, .md, .json, .xml, .csv, etc.). After loading, files are read into the browser's memory and compared locally—nothing is uploaded to any server. The "Swap" button lets you quickly reverse the comparison direction if needed.

The "ignore case" option makes the comparison case-insensitive, treating uppercase and lowercase letters as equivalent. For example, "Hello" and "hello" would be considered identical. This is useful when comparing: user-generated content where capitalization varies, case-insensitive programming languages, text where capitalization doesn't affect meaning, or when you want to focus on content changes rather than formatting. It works with word and character comparison modes but not line-by-line.