Local lab safety

Use this supplied app on your own computer for the lesson. Do not publish the intentionally unsafe starter or connect it to a real service.

Use Insert harmless demo only in this lab. It changes the visible demo marker. Do not paste it into other websites or browser consoles.

Use made-up messages, not passwords or personal information. Messages stay in this tab's memory. Author and reader are two views, not real accounts. Reload and Reset board remove messages you added and restore the two example messages.

No browser security setting needs to change. If the page does not work, ask your instructor for help.