make a proof

Every proof starts with 32 bytes. Not 31, not 33. Exactly 32. That's the size of a fingerprint made by a hash function, and a fingerprint is almost always what you should post.

hash it first. always.

A hash function is like a blender. Put the same fruit in, you get the exact same smoothie every time. But you can't look at a smoothie and get the fruit back out. That's the magic: the fingerprint proves what went in, without showing what went in.

This matters because everything on chain is public, forever. Your 32 bytes, who made the proof, when, all of it. Even after the proof closes, the history stays. So never post a secret directly. Post the hash of the secret. Reveal the secret later if you want. The hash will match, and everyone can check it.

one data, one proof

Because the address comes from the data, there can only be one live proof per 32-byte value. Try to prove the same bytes twice and the second one bounces off. Your proof owns that spot until it gets closed.

what you choose when you prove

• The data. Your 32 bytes. The whole point.
• The beneficiary. The wallet that gets the deposit back when the proof is verified. Usually you.
• The size. Three sizes: 333, 777, or 2222 bytes. Bigger sizes exist for extra notes (chapter 7). If you're not attaching notes, take the small one, it does everything.
• The timer. When the proof can be swept up. Up to 30 days out, no more. Leave it empty and you get the full 30.

what it costs

Solana makes every account hold a deposit for the space it uses. This is called rent, but it's really a refundable deposit:

The deposit isn't gone. It sits inside the proof account. When the proof gets verified, the beneficiary gets it back. When the proof expires instead, the protocol treasury takes it. That's the whole incentive: handle your proofs before the timer runs out.