Methods, systems, and apparatus, including computer programs encoded on computer-storage media, for proof of play (PoP) blockchain mining. In some implementations, a corresponding method may include providing a set of one or more task parameters for a group task to each of two or more users; responsive to a consensus among the two or more users, storing a start-task transaction that includes the set of one or more task parameters signed by each of the two or more users; storing an end-task transaction at an address of a blockchain; determining respective rewards for at least a subset of the two or more users based at least on the start-task transaction and the end-task transaction; and recording the respective rewards in the blockchain.