Coin Flip — A virtual coin flip and dice roller that uses the browser's cryptographically-secure random number generator. The result is unpredictable until the moment of the flip — no time-based trick, no pre-computed sequence. The session tracks how many heads vs tails you have seen, so you can verify the distribution over many flips.
Every flip and roll uses your browser's cryptographically-secure random number generator. Nothing is sent to a server.
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Coin Flipとは？
A virtual coin flip and dice roller that uses the browser's cryptographically-secure random number generator. The result is unpredictable until the moment of the flip — no time-based trick, no pre-computed sequence. The session tracks how many heads vs tails you have seen, so you can verify the distribution over many flips.
For coin flips, the answer is heads or tails with equal probability. For dice, the supported types are d4, d6, d8, d10, d12, d20, and d100. You can roll multiple dice at once and the tool shows each individual result plus the total.
使い方
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Click "Flip the coin"
The coin rotates for a moment, then lands on heads or tails with equal probability.
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Pick dice type and count
Choose the number of dice and the number of sides (d4, d6, d8, d10, d12, d20, d100).
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Roll and read the result
Each die shows its face. The total appears next to the individual rolls.
使用例
Quick decision
Heads we eat out, tails we cook at home.
結果： Heads — you eat out tonight.
Tabletop RPG attack roll
Roll 1d20 + 5 to hit.
結果： Roll the d20, add 5. 18+ hits most AC values.
Multiple dice
Roll 3d6 for a D&D ability score.
結果： Sum the three results. The total is between 3 and 18, with an average of 10.5.
よくある質問
関連ガイド
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A decision maker is a tiebreaker, not a replacement for judgment. Here is when it actually helps (analysis-paralysis on equal options, breaking a long deadlock, choosing between two equivalent things), and when it makes things worse (when one option is clearly better, when you have not done the analysis, when the decision matters and you need to own it).
The Math Behind a Fair Coin Flip (and Why Your Brain Lies About It)
A coin flip is the simplest random experiment. The math is 50/50, the physics is messy, and your brain is the worst part. Here is what "fair" actually means, why a flipped coin is not exactly 50/50, why 100 flips rarely show exactly 50/50, and how to verify a tool is using real randomness.
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Last reviewed: 2026-09-25