Stratum V1

The dominant protocol between pool servers and mining hardware (ASIC). Plain TCP, line-based JSON-RPC. Ad-hoc spec; no formal RFC.

Connection

[Miner] ──── TCP connect ────► [Pool]
       ──── mining.configure ─►   (optional, BIP 310)
       ◄── extension results ──
       ──── mining.subscribe ──►
       ◄── subscription_id ────
       ──── mining.authorize ─►
       ◄── true ─────────────
       ◄── mining.set_difficulty ─
       ◄── mining.notify ────────
       ──── mining.submit ────►
       ◄── true ─────────────

Key methods

mining.configure (BIP 310)

Feature negotiation, specified by BIP 310 "Stratum protocol extensions" (Informational, assigned 10 March 2018, still Draft as of September 2026). It SHOULD be the miner's first message. Its Specification section lists three extension codes - version-rolling, minimum-difficulty, subscribe-extranonce - and a fourth, info, gets a section of its own.

{"method": "mining.configure", "id": 1,
 "params": [["version-rolling"],
            {"version-rolling.mask": "1fffe000",
             "version-rolling.min-bit-count": 2}]}

The pool answers with the intersection server_mask & miner_mask. Once version-rolling is active:

• mining.submit carries a 6th parameter version_bits.
• The pool recomputes nVersion = (job_version & ~last_mask) | (version_bits & last_mask).
• mining.set_version_mask can change the mask mid-session, effective immediately.

Which bits a pool may offer tracks the reserved nVersion range: BIP 320 reserves bits 13-28 (0x1fffe000, 16 bits); BIP 323 (assigned 22 April 2026, Replaces: 320) reserves bits 5-28 (0x1fffffe0, 24 bits). Both are still Draft as of September 2026.

Without version rolling a miner can only roll the 32-bit nonce plus extranonce2; BIP 320's motivation notes hardware exhausts the nonce field in under 200 ms, which is why the extension exists.

mining.subscribe

Initial handshake. Miner gets:

• extranonce1 — pool-specific session prefix.
• extranonce2_size — bytes the miner controls in coinbase.

mining.authorize

Miner sends username (typically wallet_address.worker_name).

mining.set_difficulty

Pool tells miner the share difficulty. Lower than actual block difficulty so miners find shares frequently and pool can track contribution.

mining.notify (push)

[
    "<job_id>",
    "<prev_hash>",
    "<coinbase_part_1>",
    "<coinbase_part_2>",
    [<merkle_branches>],
    "<version>",
    "<nbits>",
    "<ntime>",
    <clean_jobs>     // boolean
]

Miner builds:

• coinbase = part1 || extranonce1 || extranonce2 || part2.
• coinbase_hash = SHA256d(coinbase).
• merkle_root = merge(coinbase_hash, merkle_branches).
• header = version || prev_hash || merkle_root || ntime || nbits || nonce.
• Iterate nonce looking for hash ≤ target.
• Periodically iterate extranonce2 too, plus the masked nVersion bits where version-rolling was negotiated.

mining.submit

When miner finds valid share:

mining.submit(["<worker>", "<job_id>", "<extranonce2>", "<ntime>", "<nonce>"])

With version-rolling negotiated, a 6th parameter version_bits follows <nonce> (BIP 310).

Pool verifies; rewards miner per share.

Pool decides everything

The fundamental issue: pool constructs the coinbase (including which transactions to include in the block). Miner just hashes what the pool sends. This means:

• Miner has no control over which txs are mined.
• Pool can censor txs.
• Miner can be tricked into signing for a different reward script.

Pool fraud risks

• Pool could lie about share difficulty (rare but possible).
• Pool could withhold rewards (very rare; reputation-driven).
• Pool could censor txs (sometimes done; OFAC compliance scenarios).

Miner endpoint config

stratum+tcp://pool.example.com:3333
username: <wallet>.<worker>
password: anything (typically "x")

Status

• Dominant: as of September 2026 Stratum V1 is still the default endpoint at essentially every pool and on every shipping ASIC; no published measurement pins the exact share down.
• Aging: clear weaknesses; Stratum V2 designed to replace.
• Compatibility: every ASIC/pool understands V1.

See also

• stratum-v2/SKILL.md
• pool-architectures/SKILL.md
• decentralized-pools/SKILL.md