Need a quick yes-or-no decision, or someone to kick off first? Flip a virtual coin: press the button and it lands on heads or tails in under a second. It is free, works on any phone or computer, and needs no sign-up.
How it works
Each flip draws a fresh random number from your browser's cryptographically secure generator (crypto.getRandomValues) and turns it into heads or tails with rejection sampling, so both sides have exactly the same 50% chance. Nothing is pre-decided and nothing is sent to a server: the toss happens on your own device. Every flip is independent. The coin has no memory, so five tails in a row do not make heads any more likely on the sixth flip. That intuition is the gambler's fallacy; the odds are 50/50 every single time.
Worked example
Two friends can't agree who drives tonight. Alex calls heads, Sam takes tails, and they agree on best of three. Flip 1 lands on tails, flip 2 on heads, flip 3 on tails: Sam wins 2–1, so Alex drives. The chance of any particular sequence of three flips, such as tails–heads–tails, is 1/2 × 1/2 × 1/2 = 1 in 8.