"Provably fair" is a claim that you can check, after the fact, that a pull came from the odds the site showed you and wasn't picked by the operator. Sites do it in one of two ways.
1. Hash commitments (server seed + client seed)
Before you open a pack, the site publishes a hash of a secret server seed. You supply (or are given) a client seed, and a counter increments with every open. The result is computed from all three. After the seed is rotated, the site reveals the server seed and you can recompute the hash and the result yourself.
Because the hash was published first, the site can't swap the seed after seeing your bet. This is common on mystery-box sites such as HypeDrop and RillaBox, and on several card rip sites.
2. Onchain randomness (VRF)
Onchain platforms use a verifiable random function, such as Chainlink VRF or Switchboard, to generate the random number on a blockchain. The draw, the proof and the result are public, so anyone can verify them. Phygitals uses VRF draws on Solana, and sites such as RipRip.io and Lastpack advertise verifiable rips.
What provably fair doesn't prove
- The odds table itself. It proves the draw matched the published odds, not that those odds are generous.
- The value of the prizes. Fair market values are set by the platform. A fair draw from an overvalued pool still loses money.
- That the card exists. For physical cards, you're relying on the vault and the grader's cert number. Look up the cert on PSA, BGS or CGC.
How to check a pull
- Before you open, note the published server seed hash and your client seed.
- After the seed rotates, copy the revealed server seed.
- Use the site's verifier, or hash the seed yourself with SHA-256, and confirm it matches what was published.
- For onchain draws, open the transaction on a block explorer and check the randomness proof.
Fairness of the draw is one check. Expected value is another: run a pack's odds through the EV calculator.