Live Buzzer — Everyone Buzzes on Their Own Phone

The one tool here that needs wifi. Open the host screen on the projector, everyone scans or types the four-character room code, and the whole room has a buzzer in their hand. The first press to reach the server wins and locks everyone else out — timed on the server in milliseconds, never on the phone, because a phone clock is wrong and a phone that lied would win every round. Nothing to install and no account: the phones just open a web page.

Open the host screenThe phone screen

Needs wifi. One of 3 tools here that run on a server instead of being a self-contained offline file. Everything else in the library is a file you keep. No wifi in the room? Use Reflex instead →

Problem

Hands go up at the same moment and nobody can honestly say who was first, so the fastest answer gets argued about instead of answered.

Who it helps

Facilitators running quick-recall rounds with a room that has wifi and phones — up to 60 people at once.

In training

Project the host screen, read the room code out, and arm the round when the question is asked. The first buzz locks the room and shows who it was and how many milliseconds after arming.

Skills shown

Cloudflare Workers, Durable Objects, WebSocket hibernation, server-authoritative timing, real-time front end.