How shuffles work at cards4.net

Our random number generator

Every deal at cards4.net is generated by Erlang's :rand module using the exsplus algorithm — a well-studied, cryptographically adequate PRNG. Each game is assigned a 63-bit integer seed. Given the same seed and game variant, the deal is always identical, so any deal can be reproduced and independently checked.

Seeds are displayed as 13-character Crockford Base32 strings (e.g. 0004FKQR2MXZE). This encoding avoids visually ambiguous characters.

Daily challenge seeds are drawn from our pre-validated solvable library — every daily is guaranteed winnable. The seed for each daily is derived deterministically from the game, variant, and UTC date, so the same deal is served to every player worldwide on that day.

See the seed format documentation for full details.

Verify a seed

Paste any seed into the verification tool on this page to see the exact deal it produces. The result is computed server-side and is identical to what you would see in the game, so you can confirm for yourself that a given seed always yields the same shuffle.