What Happens After the Ethereum Merge? Execution Layer (Eth1) and Beacon Chain (Eth2) Explained

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To prepare for Ethereum 2.0, the Ethereum Foundation announced in late January that the terms "Ethereum 1.0" (ETH1) and "Ethereum 2.0" (ETH2) would be phased out. These are now referred to as the execution layer and consensus layer, respectively. Together, they form the new Ethereum network.

The merge development is nearly complete and currently in public testing, with an expected completion date in Q2 2022. This merge represents Ethereum’s most significant upgrade yet, ensuring seamless transition for its decentralized network—keeping services uninterrupted while upgrading thousands of nodes without disrupting existing contracts or assets.

The Ethereum core developers and community have prepared extensively, and users eagerly await the changes. So, when will the merge happen, and what transformations will follow?


How the Merge Is Triggered

The Beacon Chain monitors Ethereum’s current block difficulty (total difficulty). Once this difficulty reaches or exceeds a critical threshold (TERMINAL_TOTAL_DIFFICULTY), the next block becomes the final Proof-of-Work (PoW) block. Subsequent blocks will be constructed by the Beacon Chain.


Timeline for the Merge

All preparations are complete, with the merge expected in Q2—likely by June 2022. However, delays are possible if issues arise during public testing (e.g., critical bug fixes).

The June target aligns with EIP-4345 (Arrow Glacier upgrade), which postponed the difficulty bomb to June 2022. If the merge isn’t finalized by then, another delay may occur—though the community aims to avoid this.


Ethereum After the Merge

Post-merge, Ethereum will consist of:

Architecture Overview


Execution Layer Changes

Post-merge, the execution layer removes PoW-related components while retaining core functions like EVM execution. Key updates include:

1. Block Format Modifications

2. Ether Issuance

3. Block Broadcasting

4. Engine API Integration

Three critical interfaces facilitate layer coordination:

  1. engine_newPayload: Validates ExecutionPayload (returns VALID/INVALID/SYNCING).
  2. engine_forkchoiceUpdated: Requests new block creation.
  3. engine_getPayload: Retrieves ExecutionPayload data.

Beacon Chain Post-Merge

Launched in December 2020, the Beacon Chain currently reaches consensus on empty blocks. Post-merge, it finalizes real blocks:

  1. Consensus layer triggers block creation via engine_forkchoiceUpdated.
  2. Execution layer returns a payloadId.
  3. Consensus fetches ExecutionPayload using engine_getPayload.
  4. Validates data via engine_newPayload.
  5. Finalizes with engine_forkchoiceUpdated.

FAQs

Q1: Will existing ETH1 contracts still work after the merge?
A: Yes. The execution layer ensures backward compatibility.

Q2: How does PoS replace PoW in Ethereum?
A: Validators (stakers) replace miners, reducing energy consumption by ~99.95%.

Q3: Can users stake ETH after the merge?
A: Yes—via the Beacon Chain’s staking mechanism.


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References


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