Mining Pools Controlling 75% of Bitcoin's Hashrate Back New Open Standard for Block Construction

Seven of the world's largest bitcoin mining pools have thrown their weight behind Stratum V2, an open communication protocol designed to decentralise a key function of Bitcoin mining: deciding which transactions get included in each new block.

The pools — Foundry, AntPool, F2Pool, SpiderPool, and MARA Pool among them — together account for approximately 75% of Bitcoin's total hashrate, the measure of computational power dedicated to securing the network. Their participation in the Stratum V2 working group marks one of the most significant collective endorsements the protocol has received since its development began.

What Is Stratum V2?

Stratum V2 is an updated mining communication protocol that, among other improvements over its predecessor, introduces a feature called Job Negotiation. This allows individual miners — rather than pool operators — to select which transactions they include when constructing a candidate block. Under the current dominant system, Stratum V1, pool operators make those decisions centrally on behalf of all miners contributing hashrate to their pool.

Proponents argue the change has meaningful implications for Bitcoin's censorship resistance. If pool operators control transaction selection, they can, in theory, exclude certain transactions — whether due to regulatory pressure, commercial incentives, or other motivations. Returning that control to individual miners distributes decision-making power more broadly across the network.

Industry Significance

The involvement of pools commanding 75% of global hashrate is notable because protocol adoption in Bitcoin mining has historically been slow and fragmented. Mining pools operate as businesses with their own infrastructure and incentives, and coordinating across competitors on a shared technical standard is uncommon.

The Stratum V2 working group, which includes developers, pool operators, and mining hardware manufacturers, aims to produce a common implementation that pools can adopt without each building bespoke solutions. The participation of dominant players like AntPool — operated by Bitmain, one of the largest mining hardware manufacturers — and Foundry, which has consistently ranked among the top pools by hashrate, lends the effort considerable institutional weight.

Caveats and Open Questions

Joining a working group is not the same as deploying the protocol. It remains to be seen how quickly — or whether — these pools will fully implement Stratum V2's Job Negotiation feature, which is the component most relevant to decentralising block construction. Some pools may adopt only parts of the protocol, such as its improved security and efficiency features, while retaining centralised transaction selection.

Critics of the current mining landscape have long pointed to pool concentration as a structural vulnerability for Bitcoin. While Stratum V2 offers a technical path toward greater decentralisation, its real-world impact will depend on how miners and pools choose to configure and deploy it.

Why This Matters

Network resilience: If widely adopted, Stratum V2's Job Negotiation feature could meaningfully reduce Bitcoin's vulnerability to transaction censorship, a concern that has grown as regulatory scrutiny of crypto infrastructure increases globally.
Power dynamics: The move represents a potential rebalancing of influence within Bitcoin mining, shifting authority over transaction selection away from a handful of large pool operators and toward the broader miner population.
Protocol precedent: Broad industry coordination on an open standard is relatively rare in Bitcoin mining; success here could set a template for future protocol upgrades.

Background

Bitcoin mining pools emerged as a practical solution to the statistical unpredictability of solo mining. By combining hashrate, miners earn more consistent rewards — but the trade-off has always been ceding some control to pool operators. The original Stratum protocol, introduced around 2012, became the dominant standard but was designed at a time when mining was far less concentrated and regulatory scrutiny was minimal.

Concerns about pool centralisation intensified in 2023 and 2024 as a small number of pools — many with ties to Chinese hardware manufacturer Bitmain — consistently controlled the majority of global hashrate. Researchers and Bitcoin developers flagged the theoretical risk that regulators could pressure pool operators to exclude transactions associated with sanctioned entities, effectively introducing censorship at the infrastructure level.

Stratum V2 was developed over several years by a group of Bitcoin developers and mining engineers as a comprehensive upgrade. Its adoption, however, has been gradual, with pools cautious about the engineering costs and operational changes involved.

Key Perspectives

Pool operators and mining companies: By joining the working group, major pools signal that they see Stratum V2 as the industry's direction of travel. Their participation may also reflect a desire to get ahead of regulatory risk by demonstrating commitment to a more decentralised architecture.

Bitcoin developers and decentralisation advocates: The working group's expansion is broadly welcomed as a step toward reducing systemic risk. Advocates emphasise that full adoption of Job Negotiation — not merely membership in a working group — is the metric that counts.

Critics and sceptics: Some observers caution that pool operators joining a working group carries no binding commitment. Pools could adopt performance and security improvements from Stratum V2 while quietly retaining centralised transaction selection, capturing goodwill without meaningfully changing the status quo.

What to Watch

Deployment timelines: Whether and when participating pools announce live Stratum V2 implementations, particularly the Job Negotiation module, will be the clearest measure of the initiative's substance.
Hashrate on the new protocol: Monitoring what share of global hashrate is actively mining under Stratum V2 (versus merely endorsed by pools in a working group) will reveal real adoption pace.
Regulatory developments: If regulators in major jurisdictions move to require transaction filtering at the pool level, the urgency — and political complexity — of Stratum V2 adoption would increase sharply.

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