Free Online Text Diff Checker
Compare two pieces of text instantly and find every difference with our free online diff checker. Whether you are reviewing code changes, comparing document versions, or checking edits, this tool highlights additions, deletions, and modifications at both the line and character level. Everything runs in your browser — no signup, no data stored on servers.
What Is a Diff Checker?
A diff checker (or text compare tool) analyzes two blocks of text and identifies exactly what changed between them. It shows which lines were added, removed, or modified. Advanced diff tools like this one also highlight the specific characters within a line that changed, making it easy to spot even the smallest edits.
Diff checking is essential for software development (comparing code versions), content editing (tracking changes in documents), legal review (comparing contract drafts), and any workflow where you need to see precisely what changed between two versions of text.
Features
- Side-by-Side Diff View — See original and modified text next to each other with color-coded highlights
- Inline Diff View — Single-column view showing all changes in sequence, ideal for narrow screens
- Character-Level Highlighting — See exactly which words and characters changed within modified lines
- Line Numbers — Both sides show line numbers for easy reference
- Diff Statistics — Instant count of lines added, removed, and unchanged
- Ignore Whitespace — Toggle to ignore spaces, tabs, and trailing whitespace differences
- Ignore Case — Toggle to perform case-insensitive comparison
- Copy Diff Output — Copy the diff result as a unified text diff to your clipboard
- Dark & Light Theme — Toggle for comfortable viewing in any environment
- 100% Client-Side — Your text never leaves your browser
How to Use
- Paste the original text in the left panel
- Paste the modified text in the right panel
- Click Compare to see all differences highlighted
- Toggle between Side by Side and Inline views as needed
- Use Ignore whitespace or Ignore case to refine your comparison
Frequently Asked Questions
Is my text data safe?
Yes. All comparison happens entirely in your browser using JavaScript. No text is sent to any server. Your data never leaves your machine.
What diff algorithm does this tool use?
This tool uses a Longest Common Subsequence (LCS) based diff algorithm, similar to the classic Unix diff command. It efficiently identifies the minimum set of changes between two texts.
Can I compare large files?
Yes. The tool handles texts with thousands of lines directly in the browser. For extremely large files (100,000+ lines), you may experience a brief delay during comparison.
What is the difference between side-by-side and inline mode?
Side-by-side mode shows the original and modified text in two columns, aligned by corresponding lines. Inline mode shows all changes in a single column, with removed lines followed by added lines, similar to a unified diff format.
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