## Definition

**Stratum V2** (often shortened to SV2) is a next-generation communication protocol that connects cryptocurrency miners and mining pools. It succeeds the original [Stratum Protocol](/glossary/stratum-protocol) with encrypted communication, a compact binary framing layer, and an optional job negotiation mechanism that lets miners build their own block templates.

## How It Works

In pooled [mining](/glossary/what-is-bitcoin-mining), a miner's hardware does not talk directly to the Bitcoin network. Instead, [mining software](/glossary/mining-software) connects to a pool, receives work assignments, and sends back valid [shares](/glossary/share) that prove the miner is contributing [hash power](/glossary/hash-rate). Stratum V2 keeps that workflow but redesigns the wire protocol.

**Binary framing.** Where Stratum V1 uses newline-delimited JSON text, V2 uses a compact binary format. A typical V2 message is roughly 70% smaller than its V1 equivalent, which matters for large farms running thousands of ASICs and for miners on satellite or mobile connections with limited bandwidth.

**Encryption.** V2 establishes encrypted sessions between miners and pools by default. This blocks man-in-the-middle attacks that can redirect hash power or steal valid share submissions — a real risk on V1, where all traffic is plaintext.

**Job negotiation.** This is V2's most distinctive feature. The protocol defines three roles: the Pool, the Job Declarator, and the Template Provider. A miner running a Template Provider can build a candidate block template — choosing which transactions to include — and the Job Declarator negotiates that template with the pool. The result: miners regain influence over block construction without leaving the pool.

## Why It Matters

Mining pools are central infrastructure in [proof-of-work](/glossary/proof-of-work) networks. When most miners accept pool-chosen templates wholesale, a handful of pool operators gain outsized influence over which transactions get confirmed. Job negotiation gives individual miners a path to participate in that decision, which strengthens censorship resistance.

Operationally, binary framing and encryption make pool connections both leaner and harder to tamper with. For a solo miner running a single ASIC, the bandwidth savings are modest. For a farm with ten thousand machines behind a congested uplink, they add up.

Adoption is accelerating. As of May 2026, seven mining pools representing roughly 75% of Bitcoin's hashrate have joined the SV2 Working Group, signaling that the protocol is moving from specification to production deployment.

## Related Terms

- [Stratum Protocol](/glossary/stratum-protocol)
- [Mining Software](/glossary/mining-software)
- [Share](/glossary/share)
- [Proof of Work](/glossary/proof-of-work)
- [What Is a Mining Pool?](/glossary/what-is-a-mining-pool)
- [Hash Rate](/glossary/hash-rate)