Diff Checker
Compare two texts and highlight differences line by line
Difference View
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What is a Diff Checker?
A diff checker (or diff tool) compares two blocks of text and highlights the differences between them. It shows which lines have been added, removed, or modified—making it easy to understand what changed between two versions of a document, code file, or any text.
This free online diff checker instantly compares your texts and displays results in a unified diff format, similar to what you'd see in Git or code review tools. It's perfect for code reviews, comparing document versions, or verifying configuration changes.
How to Read Diff Output
Green lines with a + symbol indicate content that was added in the modified version.
Red lines with a - symbol indicate content that was removed from the original version.
Lines without color are identical in both versions, shown for context.
Common Use Cases
Code Review
Compare code changes before committing or during pull request reviews to understand modifications.
Document Comparison
Compare legal documents, contracts, or article drafts to track edits and changes.
Configuration Changes
Verify server config updates, environment variables, or settings file modifications.
Debugging
Compare working vs broken versions of code or output to identify what changed.
Tips for Effective Comparison
- Normalize whitespace: Inconsistent indentation (tabs vs spaces) can cause false differences.
- Use the original as left: Convention places the older/original version on the left, newer on the right.
- Check line endings: Windows (CRLF) vs Unix (LF) line endings may cause every line to appear changed.
- Look for patterns: Multiple similar changes might indicate a search-and-replace operation.
Frequently Asked Questions
Is my data sent to a server?
No! All comparison happens locally in your browser. Your text never leaves your device, making it safe for sensitive content.
What algorithm is used for comparison?
This tool uses a simplified line-by-line comparison algorithm. For complex diffs with moved blocks, professional tools like Git diff use more sophisticated LCS algorithms.
Can I compare files directly?
This tool works with text content. To compare files, copy-paste their contents into the text areas. For large files, consider command-line tools like diff or GUI tools like Meld.