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Ethereum Execution Layer Specification | Ethereum Basis Weblog


  • EELS is an execution layer reference implementation in Python.
  • It is updated with mainnet.
  • It fills assessments, and passes present ones.
  • There’s an instance of an EIP applied in EELS beneath.


After greater than a yr in growth, we’re happy to publicly introduce the Ethereum Execution Layer Specification (affectionately generally known as EELS.) EELS is a Python reference implementation of the core parts of an Ethereum execution shopper centered on readability and readability. Supposed 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 assessments, 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 purchasers (which frequently combine a number of forks in the identical codepath.)

Historical past

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

Screenshot of formulas 2, 3, and 4 from the Yellow Paper
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.


As we speak, EELS is consumable as a conventional Python repository and as rendered documentation. It is nonetheless a bit tough across the edges, and would not present a lot in the best way 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 priceless 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)

    consequence = U256(left < proper)

    push(evm.stack, consequence)

    evm.laptop += 1

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

Whereas Determine 2 could be digestible to lecturers, Determine 3 is indisputably extra pure to programmers.

Here is a video walk-through of including a easy EVM instruction if that is your type of factor.

Writing Checks

It bears repeating: EELS is simply common Python. It may be examined like another Python library! Along with your complete ethereum/assessments suite, we even have a choice of pytest assessments.

With a bit of assist from execution-spec-tests, any assessments written for EELS may also be utilized to manufacturing purchasers!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 shopper 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 supplied by the creator, 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: Record[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 observe 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 wish EELS to turn out to be the default technique to specify Core EIPs, the primary place EIP authors go to prototype their proposals, and the absolute best reference for a way Ethereum works.

Should you’re inquisitive about contributing or prototyping your EIP, be a part of us on the #specs channel or seize a problem from our repository.

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