How to use it
- Tap the coin to flip it. The result is read out to screen readers, and the recent history and running tally appear underneath.
- To flip many coins at once, enter a number up to 1,000 and press Flip them: you get the heads and tails count, the percentage and the longest streak.
- For a decision that should not hang on a single toss, use Best of 3, 5 or 7.
How it works
Each flip takes one bit from crypto.getRandomValues, the Web Crypto function browsers provide for cryptographically strong random values; the site never uses Math.random for flips. One random byte gives eight flips, and every bit is equally likely to be 0 or 1 and independent of the others. The spinning animation is only decoration and is skipped if your device asks for reduced motion.
What we tested
On October 14, 2026 we ran the page’s own flip function 10 million times using the same Web Crypto API: 4,999,252 heads (49.9925%, z = -0.473); the four pairs HH, HT, TH and TT appeared equally often (chi-square 1.55 on 3 degrees of freedom), so one flip says nothing about the next; and all eight bit positions in each random byte were balanced (chi-square 3.48 on 7). The longest streak in 100,000 blocks of 100 flips matched its exact probabilities (chi-square 1.37 on 6), and 100,000 best-of-5 games split 49,739 heads to 50,261 tails with game lengths matching 1/4, 3/8 and 3/8. A deliberately broken version that reused bits failed the test. Inside Chromium the same function passed again on 2,000,000 flips (z = -1.481, pairs chi-square 4.46), and the longest streak in 2,000 blocks of 1,000 flips matched its exact distribution (chi-square 4.73). One of our 1,000-coin test batches produced 18 tails in a row; at that length the chance is about 0.37%, rare but exactly what a fair generator occasionally does. In Chromium: a tap showed the flip animation and then Tails; ten taps built a 10-flip history and tally; 1,000 coins gave 500 heads with the longest streak; best of 5 named a winner with the sequence; 5,000 coins showed a message; with reduced motion the result appeared instantly; the page fitted a 390 px phone with no errors.
| Longest streak in 100 flips | Observed (of 100,000) | Expected |
|---|---|---|
| 4 or fewer | 2,779 | 2,831 |
| 5 | 16,479 | 16,487 |
| 6 | 26,452 | 26,448 |
| 7 | 22,782 | 22,757 |
| 8 | 14,675 | 14,621 |
| 9 | 8,204 | 8,190 |
| 10 or more | 8,629 | 8,666 |
Sources
Checked on .
Frequently Asked Questions
Built by Derek Giordano · Part of Ultimate Design Tools