Swan.my.id — Jakarta — Ethereum is preparing another major change to how transactions are included in blocks. One proposal receiving significant attention is FOCIL Ethereum, short for Fork-choice Enforced Inclusion Lists.
The mechanism is designed to reduce the influence of individual block builders over which transactions are included in Ethereum blocks. Instead, a committee of validators would create inclusion lists containing transactions that should be considered for inclusion.
The proposal is particularly relevant as Ethereum's block-building ecosystem becomes increasingly specialized. While specialized builders can improve efficiency and optimize block value, their growing role also creates concerns about transaction censorship and concentration of influence.
As of September 2026, FOCIL has been selected as the consensus-layer headliner for Ethereum's planned Hegotá upgrade. However, FOCIL is not yet active on Ethereum mainnet. Hegotá remains in the planning stage, with a tentative mainnet target in the second quarter of 2027.
What Is FOCIL Ethereum?
FOCIL, or Fork-choice Enforced Inclusion Lists, is a proposed Ethereum mechanism introduced through EIP-7805.
The proposal aims to strengthen Ethereum's censorship resistance by giving a selected group of validators a role in identifying transactions that should be considered for inclusion in blocks.
At the center of the design is an inclusion list (IL). These lists contain transactions observed by selected validators through the public mempool.
The validators responsible for creating them are known as inclusion list committee members.
Block builders would still construct Ethereum blocks. However, they would no longer have complete discretion over transaction inclusion when valid transactions are covered by the relevant inclusion requirements.
FOCIL then connects these requirements to Ethereum's fork-choice mechanism. Attesters would only support blocks that satisfy the applicable inclusion-list conditions.
Therefore, FOCIL should not be interpreted as a system that makes censorship impossible. Instead, it is designed to make censorship more difficult by reducing dependence on a single block builder.
Why Does Ethereum Need FOCIL?
Ethereum has a large validator ecosystem distributed across many participants. However, validator decentralization does not automatically mean that every part of the block-building process is equally decentralized.
One area where concentration can emerge is transaction selection.
The Role of Block Builders
Ethereum's block-building architecture separates several responsibilities.
Block builders collect transactions and construct blocks while optimizing their contents for factors such as transaction fees and extractable economic value.
This specialization can make block production more efficient.
However, it can also give sophisticated builders significant influence over which transactions are ultimately included.
If a relatively small number of builders control a large share of block construction, transaction inclusion can become concentrated even when the underlying validator set remains broad.
FOCIL attempts to address this issue without removing builders from the process.
What Does Censorship Mean on Ethereum?
In the context of FOCIL, censorship does not mean deleting a transaction that is already recorded on the blockchain.
The concern occurs before a transaction becomes part of a block.
For example, a user may send a valid Ethereum transaction that enters the public mempool. A block builder can see that transaction but decide not to include it.
If the same transaction continues to be ignored by other block builders, its inclusion can be delayed.
However, not every delayed transaction represents censorship. Transactions can remain pending because of gas conditions, nonce issues, limited block capacity, network conditions, or invalid transaction data.
FOCIL specifically focuses on valid transactions that could otherwise be excluded by participants with significant influence over block construction.
How Does FOCIL Ethereum Work?
FOCIL coordinates several parts of Ethereum's architecture, including validators, inclusion-list committee members, block builders, proposers, attesters, the execution layer, and the consensus layer.
The proposed process can be summarized in several stages.
1. Validators Are Selected for the Inclusion List Committee
Under the current EIP-7805 design, 16 validators are selected for the inclusion-list committee for each slot.
Each committee member observes the public mempool through its local view of the network.
The validators then create their own inclusion lists.
Importantly, the 16 validators do not necessarily produce one identical global list. Their lists can differ because each validator may observe a different set of pending transactions.
This multi-participant structure is intended to prevent the system from simply replacing the influence of one builder with the influence of one validator.
2. Committee Members Create Inclusion Lists
Each committee member can select pending transactions from the public mempool for inclusion in its list.
The current draft does not require a single mandatory strategy for selecting transactions.
Possible approaches could consider factors such as:
- Priority fees
- How long a transaction has been pending
- Random selection
- Other protocol-compatible strategies
Each inclusion list is limited to 8 KiB of encoded transactions.
This limit helps prevent the additional mechanism from creating excessive bandwidth requirements across the Ethereum network.
Importantly, FOCIL does not require every transaction in the public mempool to appear in an inclusion list.
The list acts as a constraint on block construction rather than a complete record of every pending transaction.
3. Inclusion Lists Are Distributed Across the Network
After creating an inclusion list, committee members sign it and distribute it through Ethereum's peer-to-peer network.
Validators receiving the list perform several checks.
These checks include verifying whether:
- The creator is actually part of the committee
- The signature is valid
- The slot information is correct
- The inclusion list remains within the permitted size
A transaction does not become valid simply because it appears on an inclusion list.
Transaction validity is still checked when determining whether the block satisfies the inclusion requirements.
This distinction prevents FOCIL from becoming a mechanism for forcing invalid transactions onto the blockchain.
4. Block Builders Construct the Block
Block builders continue to perform their primary function: constructing blocks.
FOCIL does not dictate exactly where an inclusion-list transaction must appear inside a block.
Builders retain flexibility over transaction ordering as long as the applicable inclusion requirements are satisfied.
The proposed system uses a concept known as conditional inclusion.
If an inclusion-list transaction is already present in the block, the requirement is satisfied.
If it is not present, the system can evaluate whether the transaction remains valid and whether the block has sufficient capacity to include it.
A transaction that becomes invalid or cannot fit within the block does not automatically cause the entire block to fail FOCIL requirements.
This is important because FOCIL is not designed to force every transaction into a block regardless of network conditions.
5. Attesters Check Block Compliance
Attesters play a key role in enforcing FOCIL.
They retain inclusion lists received from the network and check proposed blocks against those requirements.
If the relevant transaction is already included, the requirement is satisfied.
If it is missing, the execution layer can help determine whether the transaction remains valid under the state created by transactions already included in the block.
This process can involve factors such as:
- Nonce
- Account balance
- Gas availability
- Transaction validity
- Block capacity
If a transaction remains valid and there is enough capacity, but a builder deliberately leaves it out, the block may fail to satisfy the inclusion requirement.
This is where the “Fork-choice Enforced” part of FOCIL becomes important.
Attesters would only support blocks that satisfy the relevant inclusion conditions. A block that deliberately ignores transactions that should still be included could therefore lose the attestation support needed to become part of Ethereum's canonical chain.
A Simple Example of FOCIL
Consider a user who sends a valid Ethereum transaction.
The transaction enters the public mempool and becomes visible to nodes across the network.
Without a mechanism such as FOCIL, a block builder has substantial influence over whether that transaction appears in a block it constructs.
Now suppose the builder chooses not to include it.
Under FOCIL, some validators selected as committee members may also observe the transaction. One or more committee members could add it to their inclusion lists and distribute those lists across the network.
The builder receives an additional constraint when preparing the next block.
If the transaction remains valid and there is enough block capacity, the builder is expected to accommodate the inclusion requirement.
Attesters then check the proposed block against the inclusion list.
If the builder deliberately leaves out a transaction that remains eligible for inclusion, the block may fail the relevant FOCIL requirement.
However, this does not mean every Ethereum transaction would automatically enter the next block.
Transaction validity, nonce, balance, gas, block capacity, mempool visibility, and other protocol conditions would continue to matter.
Therefore, FOCIL is better understood as a mechanism for reducing builder discretion over transaction inclusion rather than a guaranteed fast lane for every transaction.
Who Participates in FOCIL?
Several Ethereum participants and protocol components have different responsibilities under the proposed mechanism.
Users initiate the process by submitting transactions. Pending transactions can enter the public mempool and become visible to network participants.
Inclusion-list committee members are selected validators responsible for creating inclusion lists. The current EIP-7805 design specifies 16 committee members per slot.
Block builders continue to construct blocks and determine transaction ordering, but they must account for applicable inclusion-list requirements.
Proposers propose the completed block for the relevant slot.
Attesters check whether the proposed block satisfies the applicable inclusion requirements. Their votes contribute to Ethereum's fork-choice process.
The execution layer helps determine whether transactions missing from a block remain valid and eligible for inclusion.
The consensus layer handles the enforcement mechanism through fork choice and attestations.
This means FOCIL is not a wallet feature or an application that users activate directly. It is a protocol-level change to how Ethereum transaction inclusion is determined and enforced.
FOCIL vs. ePBS: What Is the Difference?
FOCIL and ePBS, or Enshrined Proposer-Builder Separation, both relate to Ethereum's block-building architecture, but they address different problems.
ePBS aims to bring proposer-builder separation directly into the Ethereum protocol.
Under EIP-7732, the relationship between proposers and builders would become more deeply integrated into the protocol rather than relying on external infrastructure in the same way as current arrangements.
FOCIL takes a different approach.
Its primary focus is transaction inclusion and censorship resistance.
The basic distinction can be summarized as follows:
- ePBS: focuses on the relationship and separation between proposers and builders.
- FOCIL: focuses on preventing excessive builder control over transaction inclusion.
- Both: contribute to Ethereum's broader effort to develop a more distributed block-construction architecture.
The two mechanisms are also being introduced on different upgrade timelines.
ePBS is associated with the planned Glamsterdam upgrade, while FOCIL has been selected for the subsequent Hegotá upgrade.
This phased approach gives Ethereum developers additional time to test changes to block construction before adding another major mechanism.
FOCIL and the Hegotá Upgrade
FOCIL has moved beyond being only a research concept.
The proposal was initially created as EIP-7805 in November 2024. By 2026, its position in Ethereum's development roadmap had become more concrete.
FOCIL was selected as the consensus-layer headliner for Hegotá, the planned Ethereum upgrade following Glamsterdam.
On September 7, 2026, the Ethereum Foundation Protocol Cluster published an evaluation of 62 EIPs proposed for Hegotá.
FOCIL was classified as an S-tier, locked-in consensus-layer headliner in that evaluation.
However, being prioritized for an upgrade does not mean the feature is already active on Ethereum mainnet.
Hegotá remains in the planning stage. Ethereum's current target is to bring the upgrade to mainnet in Q2 2027, although an exact launch date has not been confirmed.
The EIP-7805 specification also remains in Draft status, meaning technical details can still change during implementation, testing, and coordination between Ethereum clients.
Is FOCIL Already Active on Ethereum?
No.
As of September 28, 2026, FOCIL is not active on Ethereum mainnet.
The mechanism has been selected as a major consensus-layer feature for Hegotá, but the upgrade itself has not yet reached mainnet.
For users, this means Ethereum transactions currently do not receive the additional transaction-inclusion protection proposed by FOCIL.
The eventual implementation could still change before deployment because the proposal remains under development.
Therefore, descriptions of FOCIL as an active Ethereum feature would be premature. It is more accurate to describe it as a planned protocol mechanism targeted for the Hegotá upgrade.
What Could FOCIL Change for Ethereum?
The primary objective of FOCIL is to strengthen Ethereum's censorship resistance.
It does this through several related changes.
First, FOCIL reduces dependence on individual block builders for transaction inclusion. Builders continue constructing blocks, but selected validators can create constraints around eligible transactions.
Second, the mechanism gives validators a more direct role in transaction inclusion. Committee members can observe the public mempool and identify transactions through inclusion lists.
Third, FOCIL introduces stronger protocol-level enforcement. The inclusion requirement is not simply a voluntary request to builders because attesters and fork choice are involved in enforcing the rules.
Finally, FOCIL allows Ethereum to retain specialized block builders while attempting to prevent those builders from having excessive control over which valid transactions reach the blockchain.
What Does FOCIL Mean for Ethereum Users?
For ordinary Ethereum users, FOCIL would operate largely in the background.
Users would not need to activate a new wallet option or manually submit transactions to an inclusion committee.
Instead, the mechanism would change the rules followed by validators, builders, proposers, and attesters.
If implemented as currently proposed, the biggest potential change would be the additional protection given to valid transactions that are visible to the public mempool.
However, FOCIL would not eliminate every reason a transaction might remain pending.
Gas conditions, transaction validity, nonce conflicts, account balances, block capacity, network propagation, and other factors would continue to affect transaction processing.
That distinction is important when evaluating what FOCIL can and cannot accomplish.
The Bottom Line on FOCIL Ethereum
FOCIL Ethereum represents an attempt to strengthen censorship resistance without removing specialized block builders from the network.
Its design gives selected validators the ability to create inclusion lists, while attesters and Ethereum's fork-choice mechanism help enforce the resulting requirements.
The proposal therefore distributes transaction-inclusion influence across multiple participants rather than relying primarily on block builders.
As of September 2026, however, FOCIL remains a proposed protocol feature. EIP-7805 is still in Draft status, and FOCIL has not yet reached Ethereum mainnet.
Its current destination is the planned Hegotá upgrade, which is targeted for Q2 2027 without a confirmed launch date.
If the proposal reaches mainnet in its current form, FOCIL could become an important part of Ethereum's approach to transaction inclusion and censorship resistance. For now, its significance lies in the protocol design being developed and tested ahead of that potential deployment.