Mining pools are groups of cooperating miners who agree to share block rewards in proportion to their contributed mining hash power.
While mining pools are desirable to the average miner as they smooth out rewards and make them more predictable, they unfortunately concentrate power to the mining pool’s owner.
Miners can, however, choose to redirect their hashing power to a different mining pool at anytime.
Pool Concentration in China
Before we get into the best mining pools to join, it’s important to note that most mining pools are in China. Many only have Chinese websites and support. Mining centralization in China is one of Bitcoin’s biggest issues at the moment.
There are about 20 major mining pools. Broken down by the percent of hash power controlled by a pool, and the location of that pool’s company, we estimate that Chinese pools control ~81% of the network hash rate: