Coin Flip Simulator

What this simulator shows

The simulator performs a simple virtual coin toss between heads and tails. The visible output is deliberately direct: counts for each side and the sequence of results, without extra modes or analysis panels.

For a fair coin model, each flip has probability 1/2 for heads and 1/2 for tails. That does not mean every short run will split evenly. A run of 20 flips can easily land 13 heads and 7 tails, and a run of 100 can be noticeably away from 50/50 without anything strange happening.

Independent flips and the gambler’s fallacy

Each simulated flip is independent. If the last five flips were heads, the next flip is still a fresh 50/50 event. Expecting tails because it is “due” is the gambler’s fallacy.

Longer samples tend to move the overall proportion closer to 50%, but they do that by adding many new independent flips. They do not repair earlier imbalance one flip at a time.

Why streaks happen

Streaks are normal in random sequences. Several heads in a row can feel suspicious, yet it is exactly the kind of pattern that appears when independent 50/50 events are repeated. Use the sequence view to show students or teammates how random results can look less tidy than intuition expects.

Practical uses

• Choose between two low-stakes options.
• Demonstrate probability, independence and random variation.
• Generate a quick yes/no sequence for a classroom exercise.
• Compare small samples with larger samples up to 1000 flips.

Limits to keep in mind

This is a lightweight simulator, not a certified gambling or auditing system. It uses the browser’s Web Crypto random source. Results stay in page memory; in funnel mode, only the non-sensitive flip count appears in the URL. It does not require an account, file upload or installation. Refreshing the results page creates a new run rather than restoring the old sequence.