Where the numbers come from

The source

WillThisHappen currently sources its probabilities from Polymarket, one of the largest prediction markets in the world. A prediction market lets people buy and sell contracts that pay out based on whether a real-world event happens. The price of a "Yes" contract, between 0 and 1, is the market's collective estimate of the probability — because anyone who thinks it's mispriced can profit by trading against it.

We pull each market's live price, trading volume, liquidity and resolution details directly from Polymarket's public API. We are built to add more venues (such as Kalshi) over time, and will always label which source a number comes from.

How we turn markets into questions

• Binary questions("Will X happen?") show a single headline probability — the "Yes" price.
• Multi-outcome questions("Who will win?") show every outcome ranked by probability. Because each outcome is a separate market, these need not sum to exactly 100%.
• We show the 7-day change in the headline probability so you can see which way sentiment is moving, not just where it stands.

Freshness & honesty

Every question page carries an "as of"timestamp. Public pages refresh from the live market on a roughly 15-minute cadence; the API refreshes each question on request. When we can't reach the live source, we fall back to our most recent stored snapshot and label it with that snapshot's date — we never show a number without telling you how old it is, and we never invent one.

A probability is not a promise. A 70% chance still fails roughly three times in ten. Markets can be thin, slow to react, or wrong — treat these numbers as the best available estimate, not certainty.

What WillThisHappen is — and isn't

• It is a research and intelligence layer over prediction markets: read, track, export and query.
• It isn't a place to bet. You can't place a wager here, and we're not a broker, exchange or adviser.
• It isn't financial advice. Probabilities are information only.