Stratum Mining Protocol (v1)

Stratum v1 is the de facto standard protocol that connects mining hardware to a pool. It is a line-based dialect of JSON-RPC 2.0 carried over a plain TCP connection: each message is a JSON object terminated by a newline, with the miner acting as client and the pool as server. It replaced the older HTTP getwork polling model with a far more efficient push-based design.

The core message flow

A session opens when the miner sends mining.subscribe, to which the pool replies with subscription details and an extranonce. The miner then authorizes a worker with mining.authorize. From there the pool pushes work using mining.notify - which carries the job ID, previous-block hash, coinbase parts, Merkle branches, version, bits, and time - and sets the share threshold with mining.set_difficulty. When a chip finds a header beating that threshold, the miner returns it via mining.submit, and the pool accepts or rejects it.

Strengths and limits

Stratum v1's efficiency made large-scale pooled mining practical, but it has well-known shortcomings: traffic is unencrypted and unauthenticated, leaving it open to hijacking, and the pool alone chooses which transactions a block contains. Those limitations motivated a successor protocol that adds encryption and lets miners construct their own block templates. Stratum v1 nonetheless remains the most widely deployed mining protocol.

For the modern alternative and the metric pools use to size work, see the existing Stratum V2 entry and our Share Difficulty entry.