Diff Checker
Compare two texts and visualize differences instantly
Quick Examples
What is a Diff Checker?
A diff checker (also called text compare or file compare tool) is a utility that compares two pieces of text or code and highlights the differences between them. It's an essential tool for developers, writers, and anyone who needs to track changes between versions of documents or code files.
Our online diff checker uses advanced algorithms to identify additions, deletions, and unchanged content. You can compare texts line-by-line, word-by-word, or character-by-character, making it perfect for various use cases from code review to document comparison.
The tool provides a clear visual representation where additions are highlighted in green, deletions in red, and unchanged content remains neutral. You can also see similarity percentages and detailed statistics about the changes.
When to Use a Diff Checker?
Code Review
Compare different versions of code files to review changes before merging or deploying
Document Comparison
Track changes between document versions, contracts, or legal agreements
Version Control
Compare file versions before committing changes to Git or other version control systems
Content Migration
Verify that content was correctly migrated or copied from one system to another
Plagiarism Detection
Compare texts to identify similarities and potential plagiarism
How It Works
Line-Level Comparison
Our tool first compares texts line by line to identify which lines were added, deleted, or remained unchanged. This gives you a high-level overview of the changes between your texts.
Perfect for: Code files, configuration files, logs, and any structured text documents
Smart Inline Highlighting
For lines that are similar but not identical, the tool automatically highlights the specific words and tokens that changed. This word-level comparison makes it easy to spot exact differences without scanning entire lines.
Example: Changing function hello() to function hello(name) highlights only () → (name)
Side-by-Side View
Both versions are displayed side by side with synchronized line numbers. Deletions appear in the left panel (red), additions in the right panel (green), and unchanged lines in both panels for context.
Benefit: See the complete context of changes without toggling between versions
Understanding the Diff Output
Additions (Green)
Lines, words, or characters that appear in the modified text but not in the original. These represent new content that was added.
Deletions (Red)
Lines, words, or characters that appear in the original text but not in the modified version. These represent content that was removed.
Unchanged (Gray)
Content that remains identical in both texts. This helps provide context for the changes and shows what stayed the same.
Similarity Score
A percentage indicating how similar the two texts are. 100% means identical, 0% means completely different. Based on unchanged content ratio.
Frequently Asked Questions
How does the diff algorithm work?
Our diff checker uses advanced diff-match-patch algorithms to compare texts line by line, then provides word-level highlighting within changed lines. This gives you both a high-level overview of which lines changed and precise details about what changed within those lines.
What's the difference between "Ignore Whitespace" and "Ignore Case"?
"Ignore Whitespace" treats multiple spaces, tabs, and line breaks as a single space, useful when comparing code with different formatting. "Ignore Case" makes the comparison case-insensitive, so "Hello" and "hello" are considered the same. Both options help focus on content changes rather than formatting differences.
Can I compare large files?
Yes, but keep in mind that very large files (over 100,000 characters) may take longer to process since all comparison happens in your browser. For optimal performance, we recommend comparing files under 50,000 characters. All processing is done client-side, so your data never leaves your device.
How does the inline highlighting work?
When lines are similar but not identical, our tool automatically highlights the specific words or tokens that changed within those lines. For example, if you change hello() to hello(name), only the parameter change will be highlighted, making it easy to spot the exact differences.
Is my data secure?
Absolutely! All text comparison happens entirely in your browser using JavaScript. No data is uploaded to our servers or any third party. Your texts remain completely private and secure on your device. You can even use this tool offline after the page loads.
Can I export or share the diff results?
Yes! Click the "Copy Diff" button to copy the diff output to your clipboard in a standard format with + for additions, - for deletions, and spaces for unchanged lines. You can then paste this into any text editor, email, or documentation.
What do the statistics mean?
Additions shows lines added to the modified text. Deletions shows lines removed from the original. Unchanged shows identical lines. Similarity is the percentage of unchanged content. Total Changes is the sum of additions and deletions, giving you a quick view of the scope of changes.
Pro Tip
Use the "Ignore Whitespace" option when comparing code that has been reformatted or when comparing outputs from different systems that use different indentation or spacing. This helps you focus on actual content changes rather than formatting differences.