Free Online Text Diff Checker

Use Line diff when comparing structured content like code, JSON, or configuration files where changes typically span entire lines. Use Word diff when comparing prose, documentation, or when only a few words changed within otherwise identical lines — for instance, when comparing two versions of a paragraph where only names or numbers were updated. Word diff provides inline highlighting so you can see exactly which word changed without scanning the entire line.

The Text Diff Checker focuses on line, word, and character-level visual comparison with inline highlighting of differences within lines. The Diff Tool is designed to produce unified diff output in the standard patch format (with @@ -l,s +l,s @@ hunks) similar to the `diff -u` command. Use Text Diff for visual review; use Diff Tool when you need a standard patch file for applying changes.

In Line diff mode, an entire line is marked as changed if any character within it differs. This is by design — line mode compares whole lines as atomic units. To see the exact word that changed within a line, switch to Word mode, which performs a finer-grained comparison and highlights only the differing words while keeping matching words unmarked within the same line.

The tool runs entirely in your browser using the Myers diff algorithm implemented in JavaScript. Performance degrades quadratically with text size; comparing two 10,000-line files may take several seconds and can cause the browser tab to appear frozen. For files larger than 5,000 lines, consider using a native tool like `git diff`, `diff`, or a desktop diff application.

In Word mode, words are split by whitespace, so punctuation attached to a word (like "hello," or "world.") is treated as part of that word. This means "hello," vs "hello!" would show the entire token as changed. For more precise punctuation handling, use Char mode, which compares individual characters and highlights exactly which punctuation mark changed.