Every sports prediction account has a great record. That's the problem. Once the final score is in, anyone can say they called it, and the easy ways to fake a track record don't need a single lie you can point to: post the calls that came in, quietly delete the ones that didn't, nudge a number after the injury news, or write the "prediction" up after the game.

I build Clutch , an NBA app that puts one number on every game: the chance the side it favours wins. I wanted its record to be something you can check without trusting me. Here's how it works, and the code to verify it yourself.

The three things a real pregame prediction needs

A fingerprint of the numbers, published before tip. If the numbers change later, the fingerprint won't match.

A clock the forecaster can't set. A date I type proves nothing.

A record that keeps the misses. Old entries can't be swapped out or dropped.

None of this needs a blockchain. A hash function, a public Git host and a little discipline cover all three.

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