Online Text Compare & Diff Tool

Compare two texts and highlight the differences.

Comparing Text

This tool finds the differences between two pieces of text, line by line. Paste your original on the left, the modified version on the right, and see exactly what changed. Added lines show in green, removed lines in red.

Useful for comparing code versions, checking document revisions, or verifying that a file was correctly modified. The algorithm finds the longest common sequence between the texts, then shows everything else as changes.

Reading the Output

  • Green background: Lines added in the new version
  • Red background: Lines removed from the original
  • No highlight: Unchanged lines (context)

Understanding Text Comparison Algorithms

Our diff checker uses the Longest Common Subsequence (LCS) algorithm, which is the foundation of most professional diff tools including Git, SVN, and the Unix diff command. The algorithm works by finding the longest sequence of lines that appear in both texts in the same order, then highlighting everything else as additions or deletions.

The LCS algorithm operates with O(n×m) time complexity, where n and m are the lengths of the two texts being compared. This means it can efficiently handle files with thousands of lines while still providing accurate, line-by-line comparison results that developers can trust for code review and document verification.

Common Diff Use Cases

  • Code Review:Compare code changes before committing to version control systems
  • Document Versioning:Track changes between document drafts and revisions
  • Configuration Auditing:Verify changes to server configs, .env files, or settings
  • API Response Debugging:Compare expected vs actual API responses
  • Database Migration:Validate SQL schema changes before deployment
  • Legal Documents:Track contract modifications and clause changes

Frequently Asked Questions

What does the diff checker compare?

Our diff checker performs a line-by-line comparison of two text inputs. It identifies lines that are unchanged, added (present only in the modified text), or deleted (present only in the original text). Whitespace and special characters are preserved during comparison.

Is my data secure?

Yes, all processing happens on the server during your session only. We do not store, log, or retain any text you input. Your data is processed instantly and discarded after the comparison is complete.

Can I compare code files?

Absolutely! Our diff checker works with any text content including source code in any programming language, configuration files, JSON, XML, SQL queries, and more. The monospace font display ensures proper code alignment.

What do the colors mean?

Red/Pink highlights indicate lines that were deleted (present in original but not in modified). Green highlights show lines that were added (present in modified but not in original). Lines without highlighting are unchanged between the two versions.