The outcome is chosen before motion
The spin is presentation only. Turning animation off through reduced-motion settings does not change the selected side.
HEADS · TAILS · DECIDE
Coin Flip
Tap the coin or press Space. The result is selected first with browser Web Crypto, then the animation reveals it.
50/50balanced mapping
Web Cryptono Math.random fallback
localhistory stays here
FLIP NOW
One decision. One tap.
RESULTReady
Tap the coin, use the button, or press Space.
Web Crypto is unavailable in this browser, so this page will not silently fall back to weaker randomness.
Total0
Heads00%
Tails00%
Current streak0—
Longest streak0—
Balance snapshot—needs flips
RECENT HISTORY
Last 20 outcomes
No flips yet.
Customize the two choices
Decision series—
PROBABILITY LAB
Know the odds before the streak feels suspicious
probability24.609%
Exactly 5 heads in 10 fair flips.
simulation snapshot—Uses the same browser Web Crypto source.
chance the first n flips are all the same side6.25%Either all Heads or all Tails.
WHAT MATTERS
Fast enough for a decision, transparent enough for a lesson
Short runs do not need to look 50/50
Independent fair flips naturally create streaks. Ten flips can look lopsided without implying bias.
Custom labels stay binary
Rename the two sides to Yes/No or two teams; each still receives exactly half of the byte values used by the mapper.
Randomness method, exact mapping & limitations
Method
Each result requests a byte from crypto.getRandomValues(). Even byte values map to Choice 1 and odd byte values map to Choice 2. A byte has 128 even and 128 odd values, so the mapping itself is exactly balanced.
No silent fallback
If Web Crypto is unavailable, flipping is disabled rather than silently switching to Math.random().
Scope
This is browser cryptographic pseudo-randomness for everyday decisions, games, and probability learning. It is not atmospheric physical randomness, an independently audited draw, or evidence suitable for legal, gambling, prize, or other high-stakes outcomes.
Local session
Recent outcomes and custom labels are stored in this browser only so a refresh can keep your session. Reset removes the saved session.