Seven of the largest Bitcoin mining pools quietly signed onto an open protocol last week that could fundamentally reshape who actually decides what goes into each new block on the network. Foundry, AntPool, F2Pool, SpiderPool, MARA Pool, Block Inc, and DMND have joined the Stratum V2 working group, putting nearly 75% of global Bitcoin hashrate behind a standard that returns block construction decisions to individual miners rather than pool operators.
The announcement marks the most significant structural change in Bitcoin mining governance since the industry consolidated around a handful of dominant pools over the past half-decade. For years, critics have warned that while Bitcoin’s consensus mechanism theoretically distributes power across thousands of miners worldwide, the practical reality looks different: a small number of pool operators have controlled which transactions make it into blocks, creating a chokepoint that undermines the network’s censorship-resistance claims.
Stratum V2 does not fix hashrate concentration itself. Foundry still commands 34.2% of global hashrate, a figure that would make Bitcoin’s earliest advocates uncomfortable. But the protocol does address the related and arguably more pressing concern: the entity running a pool has historically decided the transaction order for every block that pool mines. Under the current Stratum V1 standard, individual miners contribute computing power but surrender the block-building decision to whoever operates their pool.
The Concentration Problem Bitcoin Has Struggled to Solve
Bitcoin mining has evolved far from the early days when enthusiasts ran mining software on home computers. The network’s total hashrate now sits at 998 exahash per second, with difficulty set to climb again on May 15 from 132.47 trillion to 135.64 trillion, per CoinWarz data. That computational arms race has driven miners into pools, where they combine resources and share block rewards proportionally to avoid the lottery-like variance of solo mining.
The pooling model works financially but creates a governance problem. When Foundry mines a block (which happens roughly once every three blocks given its 34.2% share), Foundry’s operators have traditionally decided which transactions fill that block. They choose whether to include a controversial transaction, prioritize certain fee-paying users, or potentially even coordinate with other pools to delay specific payments.
This is not a theoretical concern. In March 2023, the Bitcoin community debated whether pools should filter Ordinals inscriptions, which some miners viewed as spam. More recently, OFAC-compliant pool behavior has raised questions about whether U.S.-based operators might be pressured to exclude sanctioned addresses. The Stratum V1 architecture means these decisions sit with perhaps a dozen people globally, not the thousands of miners actually securing the network.
The Stratum V2 working group, originally founded in 2022 by Braiins and Spiral (a subsidiary of Block Inc), developed a solution: let miners construct their own block templates. Under the new protocol, individual miners decide which transactions to include based on their own criteria, while pools handle only the coordination and reward distribution. The pool operator still matters for payout mechanics, but the censorship-relevant power shifts downstream.
Why the Biggest Pools Finally Signed On
Stratum V2 has existed for nearly four years, but adoption remained limited to smaller, ideologically motivated operations. The protocol required pools to give up a meaningful power, and most saw no business reason to do so. What changed?
The working group has not disclosed what brought Foundry and AntPool to the table, but the timing aligns with several converging pressures. CoinShares estimates that up to 20% of Bitcoin miners are currently operating unprofitably, with hashprice (revenue per unit of computing power) sitting at $38.57 per petahash per second per day. That figure represents near-breakeven economics for operators running mid-generation ASIC hardware, and it is set to compress further when difficulty adjusts upward later this week.
Unprofitable miners have leverage. If a significant portion of the hashrate contributors to a pool are questioning whether to stay in the business, the pool has incentive to offer them something beyond marginally better fee structures. Stratum V2 adoption could serve as a differentiation play: miners who care about decentralization (and many do) might favor pools that let them build their own blocks.
There is also a regulatory dimension. U.S.-based pools face uncertain but plausible future pressure around transaction filtering. If a pool proactively adopts Stratum V2, it can argue that it does not control block contents, potentially insulating itself from liability for miners’ transaction choices. This is speculative, but the OFAC question has hung over American mining operations since the Tornado Cash sanctions.
MARA Holdings, the publicly traded miner behind MARA Pool, has been notably active on infrastructure and governance fronts. The company launched the MARA Foundation last month with a $100,000 grant pledge focused on open-source Bitcoin defense and quantum computing research. Joining Stratum V2 fits that positioning. Whether MARA’s 4.7% hashrate share is commercially significant matters less than the signal it sends about where large public miners see the industry heading.
Block Inc’s participation also carries weight beyond its pool’s size. Jack Dorsey’s company has positioned itself as a Bitcoin-maximalist infrastructure builder, and Spiral’s role in founding the working group means Block has skin in the game. The company’s endorsement lends credibility and potentially engineering resources to accelerate deployment.
What Actually Changes and What Remains the Same
Adoption by 75% of hashrate sounds decisive, but implementation details will determine whether Stratum V2 delivers on its promise. The protocol allows miners to construct their own block templates, but it does not require them to do so. A miner running older firmware or lacking the technical inclination could still defer to pool-provided templates, effectively recreating the V1 dynamic under a V2 label.
The working group frames last week’s announcement as the start of an accelerated deployment phase, not a switch that has already been flipped. Foundry, AntPool, and the others have joined the governance body, but the timeline for production-ready implementations across all seven pools remains unclear. Mining pool software is not trivial to update, and the largest operations will likely move cautiously to avoid service disruptions.
There is also the question of whether block template construction actually matters to most miners. The ideological case is clear: Bitcoin’s value proposition rests on censorship resistance, and censorship resistance requires distributed control over block contents. But many miners, particularly large industrial operations, view their business as a pure arbitrage between electricity costs and block rewards. They may not care deeply about which transactions their hashrate confirms, as long as the economics work.
This is where the protocol’s long-term impact becomes harder to predict. Stratum V2 creates the option for decentralized block construction, but exercising that option requires miners to run additional software and make active choices about transaction inclusion. The default behavior, even post-adoption, may trend toward passivity.
Still, the mere existence of the capability matters. If a government pressures a U.S.-based pool to filter certain transactions, miners in that pool could theoretically override the filtering by constructing their own templates. The pool would face a choice: comply with the order (and watch miners leave for non-compliant alternatives) or point to Stratum V2 as evidence that it lacks the technical ability to filter. Neither option is clean, but the second at least gives pools a legal argument.
The concentration of hashrate itself remains unaddressed. Foundry’s 34.2% share exceeds the 33% threshold that some researchers consider a soft centralization line, though actual 51% attacks require sustained coordination that a single pool’s temporary dominance does not enable. The more relevant concern has always been the combination of hashrate concentration and block construction authority in the same hands. Stratum V2 decouples those two powers, which may be the more achievable fix.
The Broader Mining Economy and What Comes Next
The announcement lands at a difficult moment for Bitcoin miners. Hashprice at $38.57 per petahash per second per day puts mid-tier operations at or below breakeven, and the upcoming difficulty adjustment will squeeze margins further. Network hashrate at 998 exahash per second represents relentless competition for a fixed supply of block rewards, and the fourth halving event reduced that supply by half in April 2024.
Miners are coping through various strategies. Some are pivoting toward AI data center services, leasing excess power and cooling capacity to hyperscalers. Others are exploring Bitcoin-backed credit instruments that let them borrow against their BTC holdings rather than selling into a weakened market. The publicly traded miners have the additional option of issuing equity, though valuations have compressed alongside the broader crypto market.
Against this backdrop, Stratum V2 adoption registers as an infrastructure investment rather than an immediate profit driver. Pools are betting that decentralized block construction will become a selling point as the industry matures and regulatory scrutiny intensifies. The miners most likely to care about the feature are also the ones most committed to staying in the business long-term, which may make them more valuable customers to cultivate.
The protocol also has implications for transaction fees, though the direction is unclear. Under Stratum V1, pools could theoretically coordinate to manipulate fee markets, excluding low-fee transactions to push up the floor. Stratum V2 makes such coordination harder since individual miners might defect and include the excluded transactions. Whether this matters in practice depends on whether miners exercise their new block-building authority or default to passive participation.
For Bitcoin as a network, the shift represents a partial answer to one of the most persistent critiques. The argument that Bitcoin is controlled by a handful of pool operators becomes harder to sustain when those operators no longer control block contents. The argument that a few companies control most of the hashrate remains valid, but that is a hardware and electricity problem, not a protocol problem.
The Stratum V2 working group positioned the announcement as a new phase of accelerated deployment, suggesting that production implementations will follow in coming months. Whether the seven signatory pools deliver on that timeline will determine whether last week’s news was a watershed moment or a press release. The infrastructure is ready. The question is whether miners will use it.
