Proof of capacity (Proof of Capacity, PoC; sometimes called Proof-of-Space) is a consensus algorithm in which the role of the main resource is played not by the computing power of processors but by the amount of free disk space. Miners fill storage drives in advance with prepared sets of data (so-called plotting), and then during the search for a block they quickly check against this data. The more space allocated, the higher the chance of earning the right to create the next block.

The main advantage of this approach is energy efficiency. Unlike proof of work, where hardware continuously performs heavy calculations, here the main load falls on hard drives, and power consumption remains low. This lowers the entry barrier: you can participate on an ordinary computer with a large drive, without specialized and expensive devices.

Additional features

• resistance to hidden mining: it is hard to imperceptibly occupy terabytes on someone else's computer;
• reuse of pre-prepared data without constant recalculations;
• more accessible participation for a wide range of users.

Among the drawbacks, increased wear on drives is noted, as well as the risk of centralization if some participants end up with especially large storage. Nevertheless, PoC is regarded as one of the "green" alternatives to energy-intensive mining.