Ethereum Execution Layer Specification


  • EELS is an execution layer reference implementation in Python.
  • It is updated with mainnet.
  • It fills checks, and passes current ones.
  • There’s an instance of an EIP carried out in EELS beneath.


After greater than a 12 months in growth, we’re happy to publicly introduce the Ethereum Execution Layer Specification (affectionately often called EELS.) EELS is a Python reference implementation of the core parts of an Ethereum execution consumer centered on readability and readability. Meant as a religious successor to the Yellow Paper that is extra programmer pleasant and up-to-date with post-merge forks, EELS can fill and execute state checks, observe mainnet1, and is a good place to prototype new EIPs.

EELS supplies full snapshots of the protocol at every fork—together with upcoming ones—making it a lot simpler to observe than EIPs (which solely suggest modifications) and manufacturing shoppers (which frequently combine a number of forks in the identical codepath.)

Historical past

Starting in 2021, as a challenge of ConsenSys’ Quilt group and the Ethereum Basis, the eth1.0-spec (because it was identified then) was impressed by the sheer frustration of getting to decipher the cryptic notation of the Yellow Paper (Determine 1) to know the precise conduct of an EVM instruction.

Determine 1. arcane runes describing the idea of the blockchain paradigm

Drawing on the profitable Consensus Layer Specification, we got down to create an identical executable specification for the execution layer.


At the moment, EELS is consumable as a traditional Python repository and as rendered documentation. It is nonetheless a bit tough across the edges, and would not present a lot in the way in which of annotations or English explanations for what numerous items do, however these will include time.

It is simply Python

Hopefully a side-by-side comparability of the Yellow Paper and the equal code from EELS can present why EELS is a beneficial complement to it:

Less-than (LT) opcode

Determine 2. Much less-than (LT) EVM instruction from Yellow Paper

def less_than(evm: Evm) -> None:
    # STACK
    left = pop(evm.stack)
    proper = pop(evm.stack)

    # GAS
    charge_gas(evm, GAS_VERY_LOW)

    outcome = U256(left < proper)

    push(evm.stack, outcome)


Determine 3. Much less-than (LT) EVM instruction from EELS

Whereas Determine 2 may be digestible to teachers, Determine 3 is indisputably extra pure to programmers.

Here is a video walk-through of adding a simple EVM instruction if that is your form of factor.

Writing Checks

It bears repeating: EELS is simply common Python. It may be examined like every other Python library! Along with the whole ethereum/tests suite, we even have a choice of pytest checks.

With a little bit assist from execution-spec-tests, any checks written for EELS will also be utilized to manufacturing shoppers!2

Exhibiting Variations

Having snapshots at every fork is nice for a sensible contract developer popping in to see the specifics of how an EVM instruction works, however is not very useful for consumer builders themselves. For them, EELS can show the variations between forks:

Screenshot of the differences in the apply_fork function between homestead and the DAO fork

Determine 4. one distinction between homestead and the DAO fork

An Instance EIP

EIP-6780 is the primary EIP to get an EELS implementation offered by the writer, Guillaume Ballet! Let’s have a look.

Screenshot of EIP-6780's specification section

Determine 5. EIP-6768’s specification part

First, we introduce a created_contracts variable to the EVM with transaction-level scope:

 class Atmosphere:
     caller: Deal with
     block_hashes: Checklist[Hash32]
     origin: Deal with
     coinbase: Deal with
     quantity: Uint
     base_fee_per_gas: Uint
     gas_limit: Uint
     gas_price: Uint
     time: U256
     prev_randao: Bytes32
     state: State
     chain_id: U64
+    created_contracts: Set[Address]

Second, we notice which contracts have been created in every transaction:

+    evm.env.created_contracts.add(contract_address)

Lastly, we modify selfdestruct so it solely works for contracts famous in created_contracts:

-    # register account for deletion
-    evm.accounts_to_delete.add(originator)
+    # Solely proceed if the contract has been created in the identical tx
+    if originator in evm.env.created_contracts:
+        # register account for deletion
+        evm.accounts_to_delete.add(originator)


We would like EELS to develop into the default technique to specify Core EIPs, the primary place EIP authors go to prototype their proposals, and the very best reference for the way Ethereum works.

In the event you’re curious about contributing or prototyping your EIP, be part of us on the #specifications channel or seize a difficulty from our repository.

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