What is Diff Checker?
A diff checker compares two blocks of text and visually highlights every difference between them — added lines, removed lines, and modified lines — making it immediately clear what changed between two versions of a document, file, or code snippet. Diff (short for difference) tools are fundamental to software development: version control systems like Git use diff algorithms to show changes between commits, code review tools highlight what changed in a pull request, and documentation tools show revisions between drafts. The Diff Checker uses the longest common subsequence (LCS) algorithm — the same algorithm underlying Git and most professional diff tools — to compute the minimal set of changes needed to transform the original text into the modified text. Added text is highlighted in green, removed text in red, and unchanged lines are shown in their original form. Both line-by-line diff (which shows entire lines as added or removed) and inline diff (which highlights the exact characters that changed within a line) modes are supported.