Spin the Wheel

How the wheel picks a winner

When you press Spin, the tool first decides where the wheel will stop. It asks the browser’s built-in cryptographic random generator (the Web Crypto API) for a random number and turns it into an angle between 0 and 360 degrees. Only then does the wheel start turning, with a few extra full rotations added so it looks like a proper spin. A smooth ease-out curve makes it race at first and creep to a stop, but the final position never changes during the animation.

The pointer sits at the top of the wheel. Whatever slice lies under it when the wheel stops is the winner. Each slice covers an equal angle — with eight entries, each one gets 45 degrees — and the stopping angle is spread evenly over the whole circle, so the chance of any slice winning is exactly one divided by the number of slices. Neither the order of the list nor where the wheel stopped last time has any effect on the next result.

Fairness and when to use it

A spinning wheel is a good fit when a group wants a choice that is visibly out of everyone’s hands: who presents first, which game to play, who buys the coffee, which student answers the next question, or a simple yes-or-no decision. Because the result is decided before the animation, there is no way to time a click to influence it.

If you need a weighted draw, list an option several times. If you need to draw without repeats, turn on winner removal. For draws with legal or financial consequences, such as official lotteries, use a process with independent witnesses and records — a web page cannot provide that kind of audit trail.

Sharing a wheel

“Copy link” turns your list into a compact code and puts it in the page address. When someone opens that link, the wheel loads with the same entries. Nothing passes through a server: the list lives entirely in the link. That also means anyone who has the link can read the entries, so avoid sharing private information this way. Links are limited to about 2,000 characters so they work in chat apps and older browsers; very long lists need to be shortened first.

Tips

• Keep labels short. The wheel shows up to about 18 characters per slice and shortens longer text, though the winner announcement always shows the full entry.
• To pick a random number, enter the numbers one per line, for example 1 to 20.
• Spin with the keyboard: move to the Spin button with Tab and press Enter or Space.
• Classroom use works well with removal turned on: paste the class list once and spin through the whole group.
• The colors are fixed and evenly spread, so neighboring slices never share a color, even with many entries.