Spin the Wheel

Why this wheel is fair, and how it decides

Most online wheels imitate a physical one: they give the wheel a random push, simulate it slowing down, and read off whichever slice ends up under the pointer. That is only as fair as the push and the physics code, and every slice boundary is a place where rounding can tip the result one way. This wheel works the other way round. When you press Spin, the winner is chosen first, with one unbiased draw over the list. Only then is the animation calculated — how many turns, and where inside the winning slice to stop — so that it lands exactly there. The spin presents a result that already exists; nothing about its speed or length can change who wins.

The draw uses crypto.getRandomValues, the generator browsers provide for cryptography, rather than Math.random. Turning its 32-bit output into a choice between, say, seven entries is where most code goes subtly wrong: taking the remainder after dividing by seven makes the first few entries a tiny bit more likely, because 2³² is not a multiple of seven. The effect is easy to see with small numbers. Pick one of six options from a random byte (0–255) and its remainder, and options one to four come up 16.80% of the time while five and six get 16.41%. The fix is rejection sampling: values from the incomplete final block are thrown away and drawn again. With it, each of N entries has a chance of exactly 1 in N — not approximately.

So the spin-length setting changes only the show, and no spin can be nudged by clicking at a particular moment or on a particular part of the wheel.

Running a giveaway people will trust

A wheel is popular for giveaways because everyone can watch the draw happen, but the method around the spin matters more than the spin. Before you draw, publish the rules: who is eligible, the closing time, how many prizes, and what happens if a winner does not reply. Then build the list from eligible entrants only.

Decide how repeated entries count. If one person commented three times and the rules say one entry per person, remove the repeats before the list goes on the wheel — the random name picker on this site can merge them for you. If extra entries are allowed, leave them in: a name on three lines has three slices and exactly three times the chance.

Draw on camera. Screen-record or livestream the spin with the list visible, and spin once per prize with 'Remove the winner before the next spin' ticked so nobody can win twice. The results list under the wheel keeps every outcome in order, and Copy puts it on your clipboard for the announcement. The one thing that destroys trust is a re-spin because the first result was inconvenient, so agree in advance that the first spin stands.

Prize draws are regulated in many countries and on most social platforms, which often require published terms and eligibility rules. A fair tool does not replace those; it makes the draw itself honest.

Classrooms, chores and everyday decisions

Teachers use a wheel to choose who answers next without the same hands going up every time. Put the class list on the wheel and tick the remove option: each student leaves the wheel once picked, so everyone gets a turn before anyone is asked twice. Leave it unticked and anyone can come up at any moment, which keeps the whole room paying attention.

The same wheel settles small, recurring arguments — whose turn it is to wash up, which film to watch, what to cook — because a visible random draw is easier to accept than whoever argues longest.

You can weight options by repeating them. An option on two lines of a ten-line list has two slices and a chance of 2 in 10, exactly 20%. It is also how to give some entrants extra chances in a raffle, and it is the only weighting the wheel has: the slices you see are precisely the odds.

Big lists, long names and accessibility

The wheel holds up to 200 entries. Labels are sized to their slice and long ones are shortened with an ellipsis. Past roughly 40 entries on a phone, or about 75 on a large screen, the slices become too thin for readable text, so labels are hidden rather than drawn as a smudge; every entry still has its own slice, and the result banner always shows the winner's full name. Entries longer than 80 characters are trimmed.

Neighbouring slices never share a colour — including the last and first, which touch — and every label colour meets the WCAG AA contrast ratio of 4.5:1 against its slice. The wheel is a real button: Tab to it and press Space or Enter to spin, and the result is announced to screen readers when it stops. If your device is set to reduce motion, the spin is skipped and the result appears at once, without confetti.

Where your list goes

Nowhere. The entries live in this browser tab and are saved in your browser's local storage, so a class list you use every week is still there next time; clearing your site data removes it. Nothing is sent to a server, so a list of students or customers never lands on anyone else's computer.

The share link is the one exception, and you control it. It copies this page's address with your list written into the part after the # sign, which is never sent to a web server when the link is opened. Anyone you give the link to will see the list, so share it only with people who should.