Stratum V2

Stratum V1, the plain text protocol pools have used since 2012, hands a miner a finished block template and asks it only to hash. V2 replaces that with a binary, encrypted protocol in four parts, one of which moves template building back to the miner. Seven pools controlling about 75 percent of network hash rate joined the working group behind it in May 2026.

How it works

Stratum V2 is four sub-protocols that can be adopted separately, which is why the upgrade has arrived in pieces rather than all at once.

The Mining Protocol carries the day to day traffic between machine and pool, replacing V1's text based JSON messages with compact binary frames. That alone saves bandwidth and cuts the round trip on new work, which reduces stale shares on slow links. The Job Declaration Protocol is the part that matters politically: it lets a miner tell the pool which block it intends to work on, rather than the other way around. The Template Distribution Protocol connects a miner's own Bitcoin Core node to its mining software, replacing the old getblocktemplate call defined in BIP22 and BIP23 with a push interface that sends updated templates the moment they change. The Job Distribution Protocol handles passing that work down to proxies and individual machines.

Encryption is the second headline change. Stratum V1 traffic is unauthenticated cleartext, which means an internet provider, a hosting facility, or anyone else in the path can read a miner's work and quietly redirect that hash rate to a pool of their own choosing. V2 wraps every connection in an authenticated encrypted channel built on the Noise handshake, so the pool a miner thinks it is talking to is the pool it is actually talking to.

The reference implementation, known as SRI, reached version 1.0.0 on March 22, 2024 and 1.1.0 that October. It ships a translation proxy so existing V1 firmware can connect to a V2 pool, which is how most of the early adoption happened. Bitcoin Core itself does not speak Stratum V2; contributors chose to expose a general mining interface over IPC instead, and the template provider lives in separate software that talks to the node through it.

Where you see it

Stratum V2 shows up first in mining infrastructure, and only indirectly in anything a bitcoin buyer touches.

DEMAND launched in 2025 as the first pool built natively on the reference implementation, Braiins, which proposed the protocol in 2019, supports it in its own pool and mining firmware, and in May 2026 Foundry, AntPool, F2Pool, SpiderPool, MARA Pool, Block, and DMND joined a working group covering roughly three quarters of network hash rate. That is a genuine shift, with one large caveat: a pool supporting job declaration does not mean its miners use it. The individual operator has to run a Bitcoin Core node and configure firmware to declare its own jobs, and that step remains uncommon.

For someone who only buys and holds, the relevance is transaction censorship. When pools build every template, a handful of companies decide which payments get confirmed, and filtering has been attempted before. Job declaration spreads that decision across thousands of independent machines, so a policy at pool level stops being a policy for the network. The upgrade does not change fees, confirmation times, or anything you see in a wallet. It changes who holds the pen.