Network
Launch Date
Consensus
Note
Sepolia
Oct 2021
PoW
Like-for-like representation of Ethereum
Görli
Jan 2019
PoA
Proof-of-Authority
Kiln
Mar 2022
PoS
Post-Merge (for ETH2), shadow fork of the mainnet
Kintsugi
Dec 2021
PoS
DEPRECATED, use Kiln; post-Merge (for ETH2)
Ropsten
Nov 2016
PoW
DEPRECATED, use Sepolia; the Merge to happen on Jun 8, 2022
Rinkeby
Apr 2017
PoA
DEPRECATED, use Görli and Görli Faucet
Kovan
Mar 2017
PoA
DEPRECATED, use Sepolia or Görli
List of active and deprecated Ethereum testnets, including Kintsugi.
Features
Optimistic rollup 
ZK-rollup 
Proof
Uses fraud proofs to prove transaction validity. 
Uses validity (zero-knowledge) proofs to prove transaction validity. 
Capital efficiency
Requires waiting through a 1-week delay (dispute period) before withdrawing funds. 
Users can withdraw funds immediately because validity proofs provide incontrovertible evidence of the authenticity of off-chain transactions. 
Data compression
Publishes full transaction data as calldata to Ethereum Mainnet, which increases rollup costs. 
Doesn't need to publish transaction data on Ethereum because ZK-SNARKs and ZK-STARKs already guarantee the accuracy of the rollup state. 
EVM compatibility
Uses a simulation of the Ethereum Virtual Machine (EVM), which allows it to run arbitrary logic and support smart contracts. 
Doesn't widely support EVM computation, although a few EVM-compatible ZK-rollups have appeared. 
Rollup costs
Reduces costs since it publishes minimal data on Ethereum and doesn't have to post proofs for transactions, except in special circumstances. 
Faces higher overhead from costs involved in generating and verifying proofs for every transaction block. ZK proofs require specialized, expensive hardware to create and have high on-chain verification costs. 
Trust assumptions
Doesn't require a trusted setup. 
Requires a trusted setup to work. 
Liveness requirements
Verifiers are needed to keep tabs on the actual rollup state and the one referenced in the state root to detect fraud. 
Users don't need someone to watch the L2 chain to detect fraud. 
Security properties 
Relies on cryptoeconomic incentives to assure users of rollup security. 
Relies on cryptographic guarantees for security. 
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--create-dirs
Ethereum
COMMITMENT LEVELS OVERVIEW

What are Ethereum commitment levels?

Learn About Safe (Justified), Finalized, and Latest Commitment Levels
Last Updated:
September 13, 2022
Table of Contents
Table of Contents
Table of Contents

{{building-on-ethereum}}

The Beacon Chain introduces two new Ethereum commitment levels, safe and finalized, that are used to label blocks alongside the existing latest, label from the PoW chain. The latest block tag is the most recent block to be added to Ethereum's blockchain, also known as the "head," the safe commitment level is one epoch (i.e. 32 slots) behind the current epoch, and the finalized commitment level is one epoch behind the most recently marked safe block.

Ethereum commitment levels are helpful because they offer useful primitives for web3 developers to query unlikely-to-reorg blocks enabled by Ethereum’s Proof-of-Stake algorithm changes. 

Because developers have higher guarantees that justified and finalized blocks are unlikely to be reorged, they can build stronger assumptions into their smart contracts and decentralized applications.

What is a block number?

The block number is a numerical value used to designate the order of a block added to the blockchain. For example, if the pending block being built and validated has a block number of 100, the most recently validated block (i.e. the latest block) would have a block number of 99. 

What is a chain re-organization (re-org)?

A chain re-organization is when a block that was added to the canonical chain (i.e. main chain, or longest chain) is removed and replaced by a different block. Reorgs impact settlement finality because blocks added to the canonical chain can be changed through a reorg.

Because reorgs can happen from exploits and as a result of Maximum Extractable Value (MEV), trusting that the latest block is settled is a difficult assumption for developers to make. 

With the migration from Proof-of-Work to Proof-of-Stake, Ethereum’s Beacon chain introduced safe and finalized block commitment levels to provide developers with stronger guarantees.

What is an epoch?

In the post-merge Ethereum environment, the Beacon Chain introduces slots, which are opportunities for new blocks to be built, and epochs which are equal to 32 slots. Because a new block can be validated exactly every 12 seconds, an epoch is equal to 6.4 minutes.

During each epoch, the Beacon Chain randomizes a committee of validators to attest to the validity of blocks being added to the blockchain. The safe and finalized block commitment levels are determined based on epochs.

While there are 32 slots in each epoch, on rare instances (less than 1%), a block might not get validated in every slot, so some epochs may have less than 32 blocks. One example is if the randomly chosen validator is not online.

What are Ethereum commitment levels?

Ethereum commitment levels are tags used to label validated blocks as either latest, justified, or finalized, which offers developers certain guarantees with regards to how likely the blocks will be reorganized. 

1. Latest

‍The latest block is the most recent block to be built and validated by Ethereum validators. The latest block should be used with caution because there are no guarantees that the Beacon Chain will not get reorganized, and this block becomes an Uncle Block, or a block that was not added to the canonical chain.

2. Safe

‍The safe block is a block that has received attestations from two-thirds of Ethereum’s validator set. Safe blocks are understood as unlikely to be reorged. 

For example, one of the few ways safe blocks could experience a chain reorganization is if there is a large-scale, coordinated attack on the network.

3. Finalized

A finalized block is a justified block that is 1 epoch behind the most recently justified block. Finalized blocks are extremely unlikely to be re-organized, with the only exception being if a two-thirds majority of validators finalize a competing chain of blocks.

How are safe and finalized commitment levels determined?

Safe and finalized commitment levels are determined by the completion of epochs. Let’s imagine the first three epochs (epoch 0, 1, and 2) after The Merge to visualize how safe and finalized blocks work.

  • Epoch 0 = blocks 0-31
  • Epoch 1 = blocks 32-63
  • Epoch 2 = blocks 64-95
  • Epoch 3 = blocks 96-127

Let’s assume the latest block is block 96, which marks the beginning of epoch 3 and the end of epoch 2.

Because block 96 includes attestations (i.e. votes from validators that signal the proposed canonical block head is true) for block 64, once the Beacon Chain receives attestations from two-thirds of the validators, block 64 is labeled as justified (safe). 

Once block 64 is labeled is justified and marked safe, the previously justified block is marked as finalized. Because safe and finalized blocks occur at the beginning of epochs, block 32 (the first block of epoch 1) is marked finalized.

Here’s another way to visualize it if the current block number is 96:

  • Block 96 (start of epoch 3) = latest
  • Block 64 (start of epoch 2) = justified (safe)
  • Block 32 (start of epoch 1) = finalized
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Ethereum
COMMITMENT LEVELS OVERVIEW

What are Ethereum commitment levels? Latest, Safe, Finalized

Learn About Safe (Justified), Finalized, and Latest Commitment Levels
Last Updated:
September 13, 2022
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Table of Contents
Table of Contents

{{building-on-ethereum}}

The Beacon Chain introduces two new Ethereum commitment levels, safe and finalized, that are used to label blocks alongside the existing latest, label from the PoW chain. The latest block tag is the most recent block to be added to Ethereum's blockchain, also known as the "head," the safe commitment level is one epoch (i.e. 32 slots) behind the current epoch, and the finalized commitment level is one epoch behind the most recently marked safe block.

Ethereum commitment levels are helpful because they offer useful primitives for web3 developers to query unlikely-to-reorg blocks enabled by Ethereum’s Proof-of-Stake algorithm changes. 

Because developers have higher guarantees that justified and finalized blocks are unlikely to be reorged, they can build stronger assumptions into their smart contracts and decentralized applications.

What is a block number?

The block number is a numerical value used to designate the order of a block added to the blockchain. For example, if the pending block being built and validated has a block number of 100, the most recently validated block (i.e. the latest block) would have a block number of 99. 

What is a chain re-organization (re-org)?

A chain re-organization is when a block that was added to the canonical chain (i.e. main chain, or longest chain) is removed and replaced by a different block. Reorgs impact settlement finality because blocks added to the canonical chain can be changed through a reorg.

Because reorgs can happen from exploits and as a result of Maximum Extractable Value (MEV), trusting that the latest block is settled is a difficult assumption for developers to make. 

With the migration from Proof-of-Work to Proof-of-Stake, Ethereum’s Beacon chain introduced safe and finalized block commitment levels to provide developers with stronger guarantees.

What is an epoch?

In the post-merge Ethereum environment, the Beacon Chain introduces slots, which are opportunities for new blocks to be built, and epochs which are equal to 32 slots. Because a new block can be validated exactly every 12 seconds, an epoch is equal to 6.4 minutes.

During each epoch, the Beacon Chain randomizes a committee of validators to attest to the validity of blocks being added to the blockchain. The safe and finalized block commitment levels are determined based on epochs.

While there are 32 slots in each epoch, on rare instances (less than 1%), a block might not get validated in every slot, so some epochs may have less than 32 blocks. One example is if the randomly chosen validator is not online.

What are Ethereum commitment levels?

Ethereum commitment levels are tags used to label validated blocks as either latest, justified, or finalized, which offers developers certain guarantees with regards to how likely the blocks will be reorganized. 

1. Latest

‍The latest block is the most recent block to be built and validated by Ethereum validators. The latest block should be used with caution because there are no guarantees that the Beacon Chain will not get reorganized, and this block becomes an Uncle Block, or a block that was not added to the canonical chain.

2. Safe

‍The safe block is a block that has received attestations from two-thirds of Ethereum’s validator set. Safe blocks are understood as unlikely to be reorged. 

For example, one of the few ways safe blocks could experience a chain reorganization is if there is a large-scale, coordinated attack on the network.

3. Finalized

A finalized block is a justified block that is 1 epoch behind the most recently justified block. Finalized blocks are extremely unlikely to be re-organized, with the only exception being if a two-thirds majority of validators finalize a competing chain of blocks.

How are safe and finalized commitment levels determined?

Safe and finalized commitment levels are determined by the completion of epochs. Let’s imagine the first three epochs (epoch 0, 1, and 2) after The Merge to visualize how safe and finalized blocks work.

  • Epoch 0 = blocks 0-31
  • Epoch 1 = blocks 32-63
  • Epoch 2 = blocks 64-95
  • Epoch 3 = blocks 96-127

Let’s assume the latest block is block 96, which marks the beginning of epoch 3 and the end of epoch 2.

Because block 96 includes attestations (i.e. votes from validators that signal the proposed canonical block head is true) for block 64, once the Beacon Chain receives attestations from two-thirds of the validators, block 64 is labeled as justified (safe). 

Once block 64 is labeled is justified and marked safe, the previously justified block is marked as finalized. Because safe and finalized blocks occur at the beginning of epochs, block 32 (the first block of epoch 1) is marked finalized.

Here’s another way to visualize it if the current block number is 96:

  • Block 96 (start of epoch 3) = latest
  • Block 64 (start of epoch 2) = justified (safe)
  • Block 32 (start of epoch 1) = finalized

The Beacon Chain introduces two new Ethereum commitment levels, safe and finalized, that are used to label blocks alongside the existing latest, label from the PoW chain. The latest block tag is the most recent block to be added to Ethereum's blockchain, also known as the "head," the safe commitment level is one epoch (i.e. 32 slots) behind the current epoch, and the finalized commitment level is one epoch behind the most recently marked safe block.

Ethereum commitment levels are helpful because they offer useful primitives for web3 developers to query unlikely-to-reorg blocks enabled by Ethereum’s Proof-of-Stake algorithm changes. 

Because developers have higher guarantees that justified and finalized blocks are unlikely to be reorged, they can build stronger assumptions into their smart contracts and decentralized applications.

What is a block number?

The block number is a numerical value used to designate the order of a block added to the blockchain. For example, if the pending block being built and validated has a block number of 100, the most recently validated block (i.e. the latest block) would have a block number of 99. 

What is a chain re-organization (re-org)?

A chain re-organization is when a block that was added to the canonical chain (i.e. main chain, or longest chain) is removed and replaced by a different block. Reorgs impact settlement finality because blocks added to the canonical chain can be changed through a reorg.

Because reorgs can happen from exploits and as a result of Maximum Extractable Value (MEV), trusting that the latest block is settled is a difficult assumption for developers to make. 

With the migration from Proof-of-Work to Proof-of-Stake, Ethereum’s Beacon chain introduced safe and finalized block commitment levels to provide developers with stronger guarantees.

What is an epoch?

In the post-merge Ethereum environment, the Beacon Chain introduces slots, which are opportunities for new blocks to be built, and epochs which are equal to 32 slots. Because a new block can be validated exactly every 12 seconds, an epoch is equal to 6.4 minutes.

During each epoch, the Beacon Chain randomizes a committee of validators to attest to the validity of blocks being added to the blockchain. The safe and finalized block commitment levels are determined based on epochs.

While there are 32 slots in each epoch, on rare instances (less than 1%), a block might not get validated in every slot, so some epochs may have less than 32 blocks. One example is if the randomly chosen validator is not online.

What are Ethereum commitment levels?

Ethereum commitment levels are tags used to label validated blocks as either latest, justified, or finalized, which offers developers certain guarantees with regards to how likely the blocks will be reorganized. 

1. Latest

‍The latest block is the most recent block to be built and validated by Ethereum validators. The latest block should be used with caution because there are no guarantees that the Beacon Chain will not get reorganized, and this block becomes an Uncle Block, or a block that was not added to the canonical chain.

2. Safe

‍The safe block is a block that has received attestations from two-thirds of Ethereum’s validator set. Safe blocks are understood as unlikely to be reorged. 

For example, one of the few ways safe blocks could experience a chain reorganization is if there is a large-scale, coordinated attack on the network.

3. Finalized

A finalized block is a justified block that is 1 epoch behind the most recently justified block. Finalized blocks are extremely unlikely to be re-organized, with the only exception being if a two-thirds majority of validators finalize a competing chain of blocks.

How are safe and finalized commitment levels determined?

Safe and finalized commitment levels are determined by the completion of epochs. Let’s imagine the first three epochs (epoch 0, 1, and 2) after The Merge to visualize how safe and finalized blocks work.

  • Epoch 0 = blocks 0-31
  • Epoch 1 = blocks 32-63
  • Epoch 2 = blocks 64-95
  • Epoch 3 = blocks 96-127

Let’s assume the latest block is block 96, which marks the beginning of epoch 3 and the end of epoch 2.

Because block 96 includes attestations (i.e. votes from validators that signal the proposed canonical block head is true) for block 64, once the Beacon Chain receives attestations from two-thirds of the validators, block 64 is labeled as justified (safe). 

Once block 64 is labeled is justified and marked safe, the previously justified block is marked as finalized. Because safe and finalized blocks occur at the beginning of epochs, block 32 (the first block of epoch 1) is marked finalized.

Here’s another way to visualize it if the current block number is 96:

  • Block 96 (start of epoch 3) = latest
  • Block 64 (start of epoch 2) = justified (safe)
  • Block 32 (start of epoch 1) = finalized

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