Is this coin flip fair?
Yes. Each toss uses your browser's cryptographic random number generator (crypto.getRandomValues), the same source used for passwords and encryption keys. Heads and tails each have exactly a 50% chance, and each flip is independent of the ones before it.
Flip many coins at once
Set the number of flips (up to 1,000) to toss them all in one go. The coin shows the last result, and the list shows every flip in order. Over many flips the split gets close to 50/50, but streaks of five or more of the same side are completely normal.
Ways to use it
Settle a choice between two options, decide who goes first in a game, pick a side for a match, or teach probability in class.