This tool uses a Longest Common Subsequence (LCS) algorithm to find the optimal alignment between two texts. It identifies lines that are equal, added, or removed, and then performs a secondary character-level diff on adjacent changed lines to highlight exactly which characters differ.

Yes, the tool can handle large texts efficiently. However, for very large files (over 10,000 lines), character-level inline diff is automatically skipped on long lines to maintain performance. All processing happens in your browser.

Unified diff is a standard text format for representing differences between files. Lines starting with '+' are additions, '-' are deletions, and ' ' (space) are unchanged context lines. The 'Copy Diff' button generates this format, which is compatible with tools like git, patch, and most code review platforms.

Absolutely. This diff checker runs entirely in your browser. No text is sent to any server. Your data stays completely private on your device.