Text Diff Viewer

Paste two versions of anything — code, config, prose — and see exactly what moved.

+42
1- function greet(name) {
2- console.log("Hello " + name);
1+ function greet(name, greeting = "Hello") {
2+ if (!name) throw new Error("name is required");
3+ console.log(`${greeting} ${name}`);
3 }4 }
4 5
5 greet("world");6 greet("world");
7+ greet("vibecoder", "Hey");

Built with this prompt

Build a text diff viewer in React with:
- Two textareas: original on the left, changed on the right
- A real line diff using longest-common-subsequence, not a naive line-by-line compare
- Side-by-side output with line numbers on both sides
- Green rows for additions, red rows for deletions, muted for unchanged
- Toggles for "ignore whitespace" and "hide unchanged lines"
- A summary count of added and removed lines
- Dark theme, no dependencies