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What Is the Builder Market in Crypto?
The Ethereum builder market is a real-time block-building auction — two firms control most of it, and your DEX swaps flow through it every time you trade.
The builder market is the competitive auction system where specialised entities called block builders assemble Ethereum transaction blocks and bid against validators to have their blocks added to the chain.
Before this layer existed, Ethereum validators handled both jobs: they selected and sequenced transactions, then proposed the resulting block to the network. That arrangement created centralisation pressure, because validators with the best MEV extraction tools earned far more than others. Proposer-Builder Separation (PBS) split the two jobs apart. Builders now focus entirely on assembling the most profitable block they can. Validators — often called proposers in this context — simply pick the highest-paying bid and sign off on it. The market between those two roles is what people mean when they say “the builder market in crypto.”
Two firms currently produce more than 86% of Ethereum blocks. Private order flow deals — not just better technology — drove that concentration. And a protocol upgrade called ePBS is on track to reshape the plumbing in late 2026. The rest of this article explains all three: how the builder market auction works, why it got this concentrated, and what is actually changing.
Key takeaways
- The builder market is Ethereum’s block-building auction layer, sitting between transaction searchers and the validators who propose blocks to the chain.
- As of early 2025, Beaverbuild and Titan Builder together produced roughly 86% of Ethereum mainnet blocks — a level of concentration well above standard “highly concentrated” thresholds.
- Private order flow — transactions routed to specific builders via private channels — is the root cause of that concentration, and it also affects every regular user making a DEX swap.
What the Builder Market Is in Crypto
A builder market is the competitive system where transaction-ordering specialists — called block builders — bid against each other in real time for the right to fill the next Ethereum block.
Before PBS arrived, Ethereum miners extracted MEV directly by reordering transactions inside blocks they produced themselves. The same dynamic carried over to proof-of-stake validators. The problem was structural: validators who invested in sophisticated transaction-selection software earned outsized returns, pushing less technical validators toward centralised staking pools. PBS was Ethereum’s architectural response.
PBS breaks the link between “who secures the chain” and “who profits from transaction ordering.” Validators no longer need to be MEV experts. They just run consensus software, accept bids from the builder market, and collect the resulting payment. Builders, meanwhile, compete in a parallel market where the only goal is assembling the most valuable block in a 12-second slot. That specialisation is efficient — but it has also produced a market structure that almost no one in Ethereum research is comfortable with.
The builder market is also where MEV reaches ordinary users. Every DEX swap, every liquidation, every cross-DEX arbitrage — all of it passes through this auction layer before landing on-chain. That makes the builder market directly relevant to anyone who trades on Ethereum, not just the researchers and validators who study it. If your swap sometimes executes at a worse price than expected, this layer is often why.
How the Builder Market Auction Works
The MEV-Boost system that runs the builder market today involves four distinct actors. Each has a specific, non-overlapping role in the block production lifecycle.
These four actors interact in sequence every time a new Ethereum slot opens:
| Actor | Role |
|---|---|
| Searchers | Find MEV opportunities (arbitrage, sandwich trades, liquidations) and submit transaction bundles to builders |
| Builders | Assemble searcher bundles plus regular mempool transactions into a complete block template, then bid to relays |
| Relays | Aggregate builder bids, verify block validity, and forward the highest-value block header to the validator |
| Validators / Proposers | Select the highest-paying bid from the relay, sign the block header, and propose the block to the Ethereum network — without seeing transaction contents first |
The order matters. Searchers feed builders. Builders bid to relays. Relays show validators only the block header, not the content. That blind commitment is critical: it stops validators from stealing the block’s MEV while also guaranteeing the builder gets paid if the block lands. The payment — the “bid” — flows directly from the builder to the validator.
MEV-Boost is currently off-chain middleware. It is not written into Ethereum’s protocol itself. Validators install MEV-Boost as an add-on, and participation is optional — though the financial incentive to participate is strong. Validators who use liquid staking protocols such as Lido or Rocket Pool are significant participants on the proposer side of this market, since those protocols run many validators that route through MEV-Boost.
The block building auction runs every 12 seconds. Each slot is its own auction. The highest bid wins, every time.
Who Builds the Blocks — The Builder Market’s Dominant Players
The Ethereum block builder market is not a crowd. As of early 2025, two firms produced the overwhelming majority of mainnet blocks.
| Builder | Market context |
|---|---|
| Beaverbuild | One of the two dominant builders; combined with Titan Builder, the pair produced approximately 86% of Ethereum blocks in early 2025 |
| Titan Builder | Rose from under 1% market share to over 40% after signing an exclusive order flow deal with Banana Gun in April 2023 |
| BuilderNet (Flashbots) | Launched November 2024 as a collaborative, decentralisation-focused alternative; migrated all Flashbots builders onto the network by December 2024 |
Titan Builder’s rise is the clearest illustration of how the current builder market works. Banana Gun is a popular DEX trading tool with a large, active user base. When Titan struck an exclusive deal to receive Banana Gun’s transaction flow before it hit the public mempool, Titan suddenly had access to high-value order flow that competing builders could not see or bid on. Market share followed. That deal alone accelerated a concentration trend that researchers had flagged for years.
Builder market shares shift faster than most people expect. Live statistics are tracked on relayscan.io, the most-used public dashboard for builder and relay data, where the breakdown updates in real time.
Flashbots’ BuilderNet was a direct response to the Beaverbuild/Titan duopoly. Rather than operating a competing centralised builder, Flashbots built a shared infrastructure network designed to let multiple smaller builders collaborate on block production and pool order flow. Whether it succeeds in fragmenting the market remains an open question as of mid-2026.
What Private Order Flow Does to the Builder Market
When you submit a transaction on a DEX without using a special routing tool, your transaction goes to the public mempool — a waiting room that every builder, searcher, and bot can see. Private order flow is the alternative: transactions routed directly to a specific builder’s private channel before they ever become public.
Users choose private routing for a practical reason: MEV protection. If a searcher can see your swap sitting in the mempool, they can front-run it and extract value at your expense. Private routing removes that exposure — but it also hands your transaction to one specific builder, concentrating order flow with whoever operates that private channel.
The feedback loop is the structural problem. More private order flow raises a builder’s winning bids. Higher winning bids attract more searchers and more private order flow deals. Incumbent builders entrench. The rotation of order flow between builders — which in a healthy market would be continuous and competitive — effectively freezes. New entrants face a steep climb: research from 2024 found that a new builder needed to subsidise bids by as much as 1.4 ETH in some periods just to gain enough market share to attract private order flow at all.
Private order flow contributed to approximately 54–60% of block value in MEV-Boost blocks during 2024–2025. That single figure explains more about builder market centralisation than any other data point. The builders who captured that flow are the builders who dominate the market. And the mechanism that captured it — offering users MEV protection via private routing — is the same mechanism creating the access barrier for everyone else.
The tension is genuine. Private routing genuinely does protect users from sandwich attacks in the short run. But in aggregate, it is also the primary driver of the centralisation that makes the builder market resemble an oligopoly more than a competitive auction.
How the Builder Market Affects Your Transactions
Every time you swap tokens on a DEX without MEV protection, a block builder decides where in the block your transaction lands. That placement has real financial consequences.
Three user-facing effects come directly from how the builder market operates:
- Sandwich attacks — bots buy a token before your swap lands, then sell immediately after, leaving you with a worse price. Daily sandwich attacks on Ethereum peaked above 4,400 per day. Extraction fell from roughly $10 million per month in late 2024 to approximately $2.5 million per month by October 2025 as MEV protection adoption spread.
- Transaction censorship — after PBS launched, builders enforcing OFAC-based compliance policies at one point produced approximately 46% of all Ethereum blocks. Transactions flagged by those policies faced nearly doubled inclusion delays, rising from around 15.8 seconds average to approximately 29.3 seconds.
- The private RPC trade-off — using Flashbots Protect or a similar private RPC genuinely reduces your sandwich attack risk. But it also routes your order flow to a dominant builder, feeding the very concentration that makes the market risky in other ways.
What can you do? Set a reasonable slippage tolerance rather than “auto” when swapping large amounts. Consider enabling a private RPC in your wallet — the MEV protection is real even if the centralisation side-effect is uncomfortable. The choice involves a genuine trade-off. Using Flashbots Protect routes your transaction away from the public mempool but feeds Beaverbuild’s order flow. Knowing that trade-off exists is the first step to making it deliberately.
Why the Builder Market Became So Centralised
Three structural forces pushed the Ethereum builder market toward concentration. They reinforce each other, which is why the market reached HHI levels of approximately 3,892 in March 2025 — well above the U.S. Department of Justice threshold of 1,800 for a “highly concentrated” market.
Winner-take-all auction dynamics are the most basic force. There is no proportional allocation in the block building auction. The builder who submits the highest bid wins the entire slot. Second place earns nothing. In any pure auction structured this way, the most efficient competitor accumulates advantage over time.
Infrastructure and latency costs compound that problem. Large builders co-locate servers near validator nodes and submit bids as close to the slot deadline as possible, maximising information advantage. A builder who submits a bid 200 milliseconds later than a competitor is effectively bidding blind. That infrastructure edge costs real money, and it creates a barrier to entry that is not just financial but technical.
The current meta for builders — securing exclusive order flow agreements with high-volume protocols — then locks the market structure in place. Once Titan Builder had Banana Gun’s flow and Beaverbuild had its own exclusive agreements, smaller builders had structurally less revenue even when submitting competitive bids. The feedback loop described above then takes over.
Together, these three forces explain why the builder market looks the way it does. None of them is the result of malice or fraud. They are the rational outcome of an auction with winner-take-all outcomes running in a market where incumbents can pay for early access to order flow.
What Is Changing — BuilderNet, ePBS, and the Glamsterdam Upgrade
The builder market is not frozen. Three significant developments — one already launched, two still in progress — are reshaping how block production works on Ethereum.
BuilderNet launched in November 2024, created by Flashbots alongside Beaverbuild and Nethermind. Its design is collaborative rather than competitive: instead of each builder running independently and hoarding order flow, BuilderNet lets participating builders pool transactions and share the resulting block value. Flashbots migrated all of its own builders onto BuilderNet and shut down its centralised builder by December 2024. The goal is to neutralise the exclusive order flow deals that drove Titan Builder’s rise and distribute MEV revenue back toward users and validators.
Enshrined PBS (ePBS), codified as EIP-7732, is the protocol-level solution. Today’s MEV-Boost relies on off-chain relays — third parties who sit between builders and validators. Relays are trusted intermediaries, and relay centralisation creates its own failure points when a small number handle the bulk of MEV-Boost traffic. EIP-7732 moves the exchange between builder and validator directly into Ethereum’s protocol, making it trustless and on-chain. No relay is needed. A new committee called the Payload Timeliness Committee (PTC) handles block propagation. The propagation window expands from roughly 2 seconds to approximately 9 seconds, giving builders more time to assemble competitive blocks.
The Glamsterdam upgrade is the Ethereum hard fork planned to include ePBS as a core EIP. Mainnet is currently targeted for H2 2026 — September to December 2026 per current devnet cadence, though that timeline is not guaranteed. Glamsterdam is also where blob-related EIPs and infrastructure changes land. Understanding blobspace and how blob fees are priced gives additional context for what the full upgrade bundle changes in Ethereum’s data layer alongside the builder market reform.
If ePBS ships on the Glamsterdam timeline, off-chain relays like MEV-Boost become optional rather than mandatory. That removes the trusted intermediary from the auction. It does not automatically break up private order flow deals between builders and DeFi protocols — those commercial relationships exist independently of the relay layer. But it does close one known attack surface and should improve censorship resistance.
Frequently Asked Questions
What is the builder market in Ethereum?
The builder market is the competitive auction system in Ethereum where specialised entities called block builders assemble transaction blocks and bid against validators to have their blocks added to the chain. It emerged from Proposer-Builder Separation (PBS) as a way to let expert builders handle transaction ordering while validators focus on consensus.
How does the builder market affect my transactions?
If you swap tokens on a DEX without MEV protection, your transaction may be visible to builders who can reorder it — a process that can result in a sandwich attack, where a bot buys before your trade and sells immediately after, leaving you with a worse price. Using a private RPC like Flashbots Protect routes your transaction to a specific builder, reducing sandwich risk, but also feeds the private order flow that has centralised the builder market.
Who controls the Ethereum builder market right now?
As of early 2025, Beaverbuild and Titan Builder together produced roughly 86% of Ethereum mainnet blocks. Flashbots’ BuilderNet, launched in November 2024, is actively working to redistribute block production, but the builder market remains heavily concentrated among a small number of players.
What is the difference between a block builder and a validator in the builder market?
A validator proposes and votes on blocks but does not assemble transaction content. A block builder is a specialised entity that selects and sequences transactions, constructs the block body, and submits a bid to the validator via a relay. The validator simply picks the highest-paying bid — without seeing block contents first — then proposes that block to the network.
Will ePBS change how the builder market works?
Yes, substantially. Enshrined PBS (EIP-7732), included in Ethereum’s Glamsterdam upgrade targeting late 2026, moves the block-building auction directly into the protocol. This removes the need for off-chain relay middleware like MEV-Boost and makes the payment from builder to validator trustless and on-chain. Off-chain relays become optional rather than required, which should reduce single points of failure and improve censorship resistance — though builder market concentration driven by private order flow deals is a separate problem that ePBS alone may not solve.
Where To Start If You Want to Track the Builder Market
Knowing the builder market exists is useful. Tracking it in practice is more useful still. Three actions will get you oriented quickly — and the third one matters more as Glamsterdam approaches.
- Check relayscan.io for live builder market share and relay statistics. This is the most-used public dashboard for builder and relay data. Builder dominance shifts over weeks, not years, and the live breakdown shows you which builders are winning slots in real time. If Beaverbuild and Titan Builder still hold over 80% combined when you check, the current concentration picture has not changed. If BuilderNet has broken into double digits, the market is beginning to fragment.
- Set a private RPC in your wallet. In MetaMask, go to Settings > Networks and add Flashbots Protect (
https://rpc.flashbots.net) as the RPC endpoint for Ethereum mainnet. This routes your transactions away from the public mempool, reducing sandwich attack exposure for DEX swaps. It will not eliminate MEV exposure entirely, but it removes the lowest-hanging attack surface. The builder market concentration trade-off is real, but the sandwich protection is also real — for most regular users, the protection wins.
- Follow EIP-7732 progress on ethereum.org/roadmap/pbs for technical status updates. Glamsterdam is in final devnet stages as of mid-2026, but mainnet date is not confirmed. If the timeline slips, the current MEV-Boost-based builder market continues operating unchanged. When ePBS does land, off-chain relays become optional — which is when the market structure has the clearest chance to shift.
