Free Text Diff Checker Online

Text Diff compares two blocks of text and highlights the differences between them. This is useful when reviewing changes — you paste the original text and the updated version, and the tool shows exactly which lines were added, removed, or kept. The output uses color coding: green for additions, red for deletions, and grey for unchanged text. Diff is the core mechanism behind how version control systems like Git track changes.

The tool uses the Myers diff algorithm to find the longest common subsequence between the two texts. Each line is classified as unchanged, added, or removed. The algorithm is O(ND) where N is the total number of lines and D is the length of the edit script, making it efficient even for large documents.