Introduction
Ethereum transaction inclusion strategies refer to the methods by which users and validators determine which transactions are added to a block and in what order, especially given the network's shift to proof-of-stake in September 2022. These strategies have evolved from simple gas-price bidding to complex mechanisms involving maximum extractable value (MEV), private relays, and block-building auctions. The rise of proposer-builder separation (PBS) has fundamentally altered how transactions are prioritized, introducing both efficiencies and new risks. This article provides a neutral, fact-led examination of these strategies, their intended benefits, inherent risks, and the alternatives available to market participants.
The Evolution of Transaction Inclusion in Ethereum
Before the Merge, Ethereum relied on a first-price auction model: users submitted transactions with a gas price, and miners selected the highest-paying ones. This system was straightforward but incentivized users to overpay for quick inclusion, especially during network congestion. After the shift to proof-of-stake, validators replaced miners, but the core problem of transaction ordering remained. The introduction of MEV—the value extracted by reordering, including, or excluding transactions—led to the development of specialized strategies. Validators now use block builders that bundle transactions into blocks, often relying on MEV-Boost, an open-source middleware that facilitates PBS. Under PBS, block proposers (validators) outsource block construction to specialized builders who compete in an auction to present the most profitable block. This separation aims to democratize MEV extraction and reduce centralization pressures on validators.
Key Transaction Inclusion Strategies
Several distinct strategies have emerged for users and validators seeking to manage transaction inclusion. The first and most basic is the priority gas auction (PGA), where users compete to raise their gas price for faster confirmation. While still used, PGAs are increasingly inefficient because they reward bots optimized for speed rather than human users. A second approach relies on private transaction relays, such as Flashbots Protect or Eden Network, which submit transactions directly to validators or builders, bypassing the public mempool. These relays prevent frontrunning by keeping transaction data private until inclusion. A third strategy involves using MEV-aware wallets, which integrate with relays and simulate outcomes before submission.
For validators, the dominant strategy is to use MEV-Boost to accept blocks from external builders. As of early 2025, over 90% of Ethereum blocks are built by relays via PBS, according to data from Flashbots. Validators can also choose to build blocks themselves using software like Decentralized Exchange Risks, but this requires sophisticated infrastructure to compete with professional builders. Some validators adopt a "do-not-include" strategy, where they reject certain builder blocks to avoid perceived risks, though this reduces their revenue. These strategies collectively aim to optimize for inclusion, timing, and profit, but each carries trade-offs.
Benefits of Current Inclusion Strategies
The primary benefit of strategies like PBS and private relays is improved efficiency. By separating block proposal from block construction, PBS reduces the ability of large validators to dominate MEV extraction. Data from the Ethereum Foundation shows that PBS has lowered the variance in validator rewards, making staking more predictable. Private relays also reduce the risk of frontrunning, a form of MEV where an adversary places a transaction before a user's pending trade to profit from price movements. For example, a user sending a large trade to a decentralized exchange can use a relay to avoid having their transaction copied and reversed.
Additionally, these strategies have encouraged competition among block builders. In 2024, over 20 independent builders competed for blocks, driving down builder margins and increasing the share of MEV returned to validators. This competition has resulted in more affordable inclusion for ordinary users. The Ethereum Transaction Ordering Fairness debate has also advanced, as advocates argue that PBS creates a more level playing field for transaction ordering decisions. Another benefit is transparency: MEV-Boost is open-source, and relayers publish data on block content, allowing researchers to analyze ordering patterns and detect malicious behavior.
Risks and Downsides
Despite their benefits, current inclusion strategies introduce significant risks. One major concern is centralization of block construction. While PBS was designed to decentralize validation, it has concentrated block-building power among a few sophisticated entities. As of early 2025, the top three builders (Titan, Flashbots, and Rsync) produce over 70% of blocks, raising fears of censorship or market manipulation. If these builders collude or face regulatory pressure, they could exclude transactions from specific protocols or wallets.
Another risk arises from relay failures. In October 2024, a major relay outage caused delays in block production, leading to missed slots and lost validator revenue. Users relying on private relays also face counterparty risk, as relay operators can see transaction data before inclusion, even if they promise not to exploit it. Additionally, the complexity of these systems opens up software bugs. A 2023 error in an MEV-Boost relay caused an estimated $20 million in lost value due to incorrect transaction ordering. These risks force users and validators to carefully weigh the benefits of advanced inclusion strategies against potential losses.
Moreover, the fairness of transaction ordering remains contested. While some argue that PBS improves neutrality, others point out that builders still prioritize profitable transactions over time-sensitive ones like liquidations or governance votes. This can lead to systematic bias where retail users face higher costs or slower inclusion. The reliance on searchers—specialized bots that hunt for MEV—also creates an arms race in infrastructure, favoring large capital participants. As one validator operator noted, "The current system rewards those who can afford the fastest relay connections, not necessarily those with the most valuable transactions."
Alternatives to Current Strategies
Several alternatives are being developed to address the risks described above. One prominent alternative is the adoption of commit-reveal schemes, where users commit to a transaction hash in advance and only reveal the details later. This scheme, used by protocols like Aztec and Succinct, prevents frontrunning by making transaction data unreadable until inclusion. However, commit-reveal adds latency and complexity, as users must submit two transactions instead of one.
Another approach is the use of decentralized ordering protocols, such as Fair Sequencing Services (FSS) or the Verkle Trie-based proposals from the Ethereum Foundation. FSS aims to remove ordering power from validators and builders entirely, replacing it with a deterministic, verifiable sequencing mechanism. While promising in theory, FSS implementations are still experimental and face scalability challenges. A more immediate alternative is to rely on layer-2 solutions, such as rollups, which batch transactions before submitting them to Ethereum. On layer-2, transaction ordering is handled by sequencers, often centralized but with plans for decentralization. Arbitrum and Optimism have both introduced decentralized sequencer tests, though adoption remains limited.
For individual users, a practical alternative is to use multi-relay or multi-builder strategies. Tools like MEV Blocker combine multiple private relays to reduce dependence on any single operator. Similarly, wallets that simulate transaction outcomes across different relays can help users choose the most favorable inclusion terms. Finally, some validators advocate for a return to simpler fee markets, such as the EIP-1559 base fee mechanism, which automatically adjusts block capacity with demand. While EIP-1559 improved fee predictability, it does not address ordering manipulation, meaning it must be combined with other strategies to achieve fair inclusion.
The Future of Transaction Inclusion
The landscape of Ethereum transaction inclusion will likely continue evolving as researchers and developers respond to identified risks. One proposed upgrade is inclusion lists, where validators enforce the inclusion of pre-specified transactions in blocks to prevent censorship by builders. The Ethereum Foundation is also exploring "PBS with private order flow," which would allow users to submit transactions directly to validators without relying on relays, potentially reducing centralization. Meanwhile, the growing use of account abstraction (ERC-4337) could give users programmatic control over fee payments and inclusion policies, enabling custom strategies like paying extra for ordering guarantees.
Regulatory developments also pose uncertainties. If governments impose know-your-customer (KYC) requirements on validators or relays, transaction inclusion could become subject to compliance checks, fundamentally altering the open nature of Ethereum. Some builders have already started filtering transactions to avoid interactions with sanctioned addresses. As one industry analyst put it, "Transaction inclusion is becoming a geopolitical issue, not just a technical one." For now, the most robust strategy for users is to remain informed and diversify their inclusion methods—balancing speed, cost, and privacy.
Conclusion
Ethereum transaction inclusion strategies have advanced significantly from simple gas auctions to the multi-layered, MEV-driven ecosystems of PBS and private relays. These strategies offer clear benefits in efficiency, transparency, and frontrunning protection. However, they also introduce risks of centralization, relay failures, and ordering fairness concerns. Alternatives such as commit-reveal schemes, FSS, and layer-2 sequencing are emerging, but none have achieved widespread adoption. As Ethereum continues its maturation, the challenge will be to balance innovation with decentralization, ensuring transaction inclusion remains accessible and fair for all participants. Users and validators must carefully evaluate these trade-offs to select strategies that align with their specific needs, while keeping an eye on the evolving regulatory and technical landscape.