Skip to main content

Try it Live

Run Hardfork examples in the interactive playground

​
Hardfork Timeline

Complete list of Ethereum hardforks with dates, features, and EIP changes.

​
Overview

Each hardfork represents a protocol upgrade that changes EVM behavior, gas costs, or adds new features. Hardforks build upon previous ones chronologically. 
import { FRONTIER, CANCUN, PRAGUE } from 'tevm';

​
Hardfork Constants

All hardforks exported as constants: 
export const FRONTIER: BrandedHardfork
export const HOMESTEAD: BrandedHardfork
export const DAO: BrandedHardfork
export const TANGERINE_WHISTLE: BrandedHardfork
export const SPURIOUS_DRAGON: BrandedHardfork
export const BYZANTIUM: BrandedHardfork
export const CONSTANTINOPLE: BrandedHardfork
export const PETERSBURG: BrandedHardfork
export const ISTANBUL: BrandedHardfork
export const MUIR_GLACIER: BrandedHardfork
export const BERLIN: BrandedHardfork
export const LONDON: BrandedHardfork
export const ARROW_GLACIER: BrandedHardfork
export const GRAY_GLACIER: BrandedHardfork
export const MERGE: BrandedHardfork
export const SHANGHAI: BrandedHardfork
export const CANCUN: BrandedHardfork
export const PRAGUE: BrandedHardfork
export const OSAKA: BrandedHardfork

export const DEFAULT: BrandedHardfork  // PRAGUE

​
Complete Timeline

​
FRONTIER (July 2015)

Original Ethereum launch Initial release with base EVM functionality. Key Features:
  • Basic EVM opcodes (ADD, MUL, SSTORE, SLOAD, etc.)
  • Contract creation and execution
  • Mining with Ethash PoW
  • Gas mechanism
Status: Foundation for all future hardforks

​
HOMESTEAD (March 2016)

First planned hardfork Fixed critical issues and added DELEGATECALL. Key Features:
  • DELEGATECALL opcode (0xF4) - Execute code in caller’s context
  • Difficulty adjustment improvements
  • Gas cost changes for transaction creation
  • Contract creation cost changes
EIPs:
  • EIP-2: Homestead hard fork changes
  • EIP-7: DELEGATECALL opcode

​
DAO (July 2016)

Emergency fork for DAO hack State-only changes, no EVM modifications. Key Features:
  • Moved funds from compromised DAO contract
  • No opcode or gas changes
  • Controversial hard fork (created Ethereum Classic split)
Status: Historical significance, no protocol changes

​
TANGERINE_WHISTLE (October 2016)

Gas repricing fork Increased gas costs for IO-heavy operations after DoS attacks. Key Features:
  • Increased gas cost for EXTCODESIZE, EXTCODECOPY, BALANCE, SLOAD
  • Changed gas cost for SUICIDE/SELFDESTRUCT
  • Maximum call depth increased
EIPs:
  • EIP-150: Gas cost changes for IO-heavy operations
  • EIP-158: State clearing

​
SPURIOUS_DRAGON (November 2016)

State cleaning fork Removed empty accounts and added replay protection. Key Features:
  • Empty account removal (state cleaning)
  • EXP opcode repricing
  • Contract code size limit (24KB)
  • Replay attack protection
EIPs:
  • EIP-155: Simple replay attack protection
  • EIP-160: EXP cost increase
  • EIP-161: State trie clearing
  • EIP-170: Contract code size limit

​
BYZANTIUM (October 2017)

Major feature fork Added important opcodes for smart contract functionality. Key Features:
  • REVERT opcode (0xFD) - Revert with error message
  • RETURNDATASIZE (0x3D) and RETURNDATACOPY (0x3E)
  • STATICCALL opcode (0xFA) - Non-state-changing calls
  • Modified difficulty adjustment (ice age delay)
  • zkSNARK precompiles
EIPs:
  • EIP-140: REVERT instruction
  • EIP-211: RETURNDATASIZE and RETURNDATACOPY
  • EIP-214: STATICCALL opcode
  • EIP-658: Embedding transaction status in receipts
  • EIP-196: zkSNARK precompile (alt_bn128 addition)
  • EIP-197: zkSNARK precompile (alt_bn128 multiplication)
  • EIP-198: BigInt modular exponentiation precompile

​
CONSTANTINOPLE (February 2019)

Efficiency improvements Added CREATE2 and bitwise shift opcodes. Key Features:
  • CREATE2 opcode (0xF5) - Deterministic contract addresses
  • SHL (0x1B), SHR (0x1C), SAR (0x1D) - Bitwise shift operators
  • EXTCODEHASH opcode (0x3F) - Get contract code hash
  • Gas cost optimizations
EIPs:
  • EIP-1014: CREATE2 opcode (Skinny CREATE2)
  • EIP-145: Bitwise shifting instructions
  • EIP-1052: EXTCODEHASH opcode
  • EIP-1234: Constantinople difficulty bomb delay

​
PETERSBURG (February 2019)

Quick fix fork Removed EIP-1283 due to reentrancy concerns. Deployed simultaneously with Constantinople after delay. Key Features:
  • Removed EIP-1283 (net gas metering for SSTORE)
  • All other Constantinople features retained
EIPs:
  • EIP-1283: Removed (was net gas metering for SSTORE)
Note: Petersburg = Constantinople - EIP-1283

​
ISTANBUL (December 2019)

Gas optimization fork Rebalanced SSTORE gas costs and added new opcodes. Key Features:
  • CHAINID opcode (0x46) - Get current chain ID
  • SELFBALANCE opcode (0x47) - Get contract’s own balance (cheaper than BALANCE)
  • SSTORE gas cost rebalancing (EIP-2200)
  • Gas cost reductions for SNARKs and STARKs
  • Blake2 compression precompile
EIPs:
  • EIP-152: Blake2 precompile
  • EIP-1108: Reduce alt_bn128 precompile gas costs
  • EIP-1344: CHAINID opcode
  • EIP-1884: Repricing for trie-size-dependent opcodes
  • EIP-2028: Calldata gas cost reduction
  • EIP-2200: Net gas metering for SSTORE (reintroduced safely)

​
MUIR_GLACIER (January 2020)

Difficulty bomb delay Delayed ice age, no EVM changes. Key Features:
  • Difficulty bomb delayed 4,000,000 blocks
  • No opcode changes
  • No gas cost changes
EIPs:
  • EIP-2384: Muir Glacier difficulty bomb delay
Status: Administrative fork, no protocol changes

​
BERLIN (April 2021)

Access list fork Gas cost changes for state access patterns. Key Features:
  • Cold/warm storage access distinction
  • Increased gas costs for SLOAD, CALL, BALANCE, EXT operations on first access
  • Optional access lists in transactions (Type 1)
  • MODEXP precompile gas cost changes
EIPs:
  • EIP-2565: ModExp gas cost
  • EIP-2718: Typed transaction envelope
  • EIP-2929: Gas cost increases for state access opcodes
  • EIP-2930: Optional access lists
Impact: Changed gas costs for many operations

​
LONDON (August 2021)

Fee market reform Introduced EIP-1559 base fee mechanism. Key Features:
  • EIP-1559: Base fee + priority fee transaction pricing
  • BASEFEE opcode (0x48) - Get current block’s base fee
  • Base fee burned (deflationary mechanism)
  • Type 2 transactions (EIP-1559)
  • Ice age delay
EIPs:
  • EIP-1559: Fee market change for ETH 1.0 chain
  • EIP-3198: BASEFEE opcode
  • EIP-3529: Reduction in refunds
  • EIP-3541: Reject new contracts starting with 0xEF
  • EIP-3554: Difficulty bomb delay
Impact: Fundamental change to transaction fee mechanism

​
ARROW_GLACIER (December 2021)

Difficulty bomb delay Delayed ice age before Merge, no EVM changes. Key Features:
  • Difficulty bomb delayed ~6 months
  • No opcode changes
  • No gas cost changes
EIPs:
  • EIP-4345: Difficulty bomb delay
Status: Administrative fork preparing for Merge

​
GRAY_GLACIER (June 2022)

Difficulty bomb delay Further delayed ice age before Merge, no EVM changes. Key Features:
  • Difficulty bomb delayed 700,000 blocks
  • No opcode changes
  • No gas cost changes
EIPs:
  • EIP-5133: Difficulty bomb delay
Status: Final delay before Merge

​
MERGE (September 2022)

Proof of Stake transition Historic transition from Proof of Work to Proof of Stake. Key Features:
  • Proof of Stake consensus - No more mining
  • PREVRANDAO opcode (replaces DIFFICULTY, still 0x44)
  • Beacon chain integration
  • DIFFICULTY opcode returns PREVRANDAO value
  • Block structure changes
EIPs:
  • EIP-3675: Upgrade consensus to Proof of Stake
  • EIP-4399: Supplant DIFFICULTY with PREVRANDAO
Aliases: “Paris” (consensus layer name) Impact: Fundamental change from PoW to PoS

​
SHANGHAI (April 2023)

Withdrawal enabling fork Enabled staking withdrawals and added PUSH0. Key Features:
  • EIP-3855: PUSH0 opcode (0x5F) - Push constant 0 onto stack
  • Staking withdrawals enabled
  • Warm COINBASE (EIP-3651)
EIPs:
  • EIP-3651: Warm COINBASE
  • EIP-3855: PUSH0 instruction
  • EIP-3860: Limit and meter initcode
  • EIP-4895: Beacon chain push withdrawals
Impact: Enabled staking withdrawals, gas savings with PUSH0

​
CANCUN (March 2024)

Proto-danksharding fork Introduced blob transactions for L2 scalability. Key Features:
  • EIP-4844: Blob transactions (Type 3) - Proto-danksharding
  • BLOBHASH opcode (0x49) - Access blob versioned hashes
  • BLOBBASEFEE opcode (0x4A) - Get blob gas base fee
  • EIP-1153: Transient storage - TLOAD (0x5C) and TSTORE (0x5D)
  • EIP-5656: MCOPY opcode (0x5E) - Memory copy instruction
  • Point evaluation precompile for KZG commitments
EIPs:
  • EIP-1153: Transient storage opcodes (TLOAD/TSTORE)
  • EIP-4844: Shard blob transactions (proto-danksharding)
  • EIP-4788: Beacon block root in EVM
  • EIP-5656: MCOPY instruction
  • EIP-6780: SELFDESTRUCT only in same transaction
  • EIP-7516: BLOBBASEFEE opcode
Impact: Major scalability improvement for L2s via cheap blob data

​
PRAGUE (May 2025)

Prague-Electra fork Current default. BLS cryptography and account abstraction features. Key Features:
  • EIP-2537: BLS12-381 curve precompiles (10 new precompiles)
  • EIP-7702: Set EOA code for one transaction (account abstraction)
  • Validator set changes (EIP-7251, EIP-7002)
  • MaxEB (Maximum effective balance increase)
EIPs:
  • EIP-2537: BLS12-381 curve operations precompiles
  • EIP-7002: Execution layer triggerable exits
  • EIP-7251: Increase max effective balance
  • EIP-7702: Set EOA account code for one transaction
  • EIP-2935: Serve historical block hashes from state
Status: Current default hardfork Impact: Enables native account abstraction patterns, BLS signatures

​
OSAKA (TBD)

Future fork Planned improvements to ModExp and transaction limits. Key Features:
  • EIP-7883: ModExp gas increase for large inputs
  • EIP-7823: ModExp upper bounds
  • Transaction and block limits
EIPs:
  • EIP-7883: ModExp gas increase
  • EIP-7823: ModExp upper bounds
  • EIP-7825: Transaction gas limit cap
  • EIP-7934: Block RLP limit
Status: Planned, not yet deployed

​
Summary Tables

​
Consensus Changes

HardforkConsensusChange
Frontier - Gray GlacierProof of WorkEthash mining
Merge+Proof of StakeBeacon chain validators

​
Major Opcode Additions

HardforkOpcodesPurpose
HomesteadDELEGATECALLExecute in caller context
ByzantiumREVERT, STATICCALLError handling, view functions
ConstantinopleCREATE2, SHL/SHR/SARDeterministic addresses, shifts
IstanbulCHAINID, SELFBALANCEChain ID, gas optimization
LondonBASEFEEEIP-1559 base fee
MergePREVRANDAO (replaces DIFFICULTY)PoS randomness
ShanghaiPUSH0Gas savings
CancunTLOAD/TSTORE, MCOPY, BLOBHASHTransient storage, blobs

​
Feature Timeline

FeatureHardforkEIP
DELEGATECALLHomesteadEIP-7
REVERTByzantiumEIP-140
STATICCALLByzantiumEIP-214
CREATE2ConstantinopleEIP-1014
CHAINIDIstanbulEIP-1344
Access ListsBerlinEIP-2930
EIP-1559LondonEIP-1559
Proof of StakeMergeEIP-3675
PUSH0ShanghaiEIP-3855
Blob TransactionsCancunEIP-4844
Transient StorageCancunEIP-1153
BLS PrecompilesPragueEIP-2537

​
Usage

import {
  FRONTIER, HOMESTEAD, BYZANTIUM, CONSTANTINOPLE,
  ISTANBUL, BERLIN, LONDON, MERGE, SHANGHAI, CANCUN,
  PRAGUE, OSAKA, DEFAULT
} from 'tevm';

// Use constants directly
console.log(CANCUN);  // "cancun"

// Compare versions
import { isAtLeast } from 'tevm';
isAtLeast(CANCUN, LONDON);  // true

// Check features
import { hasEIP4844 } from 'tevm';
hasEIP4844(CANCUN);  // true
hasEIP4844(SHANGHAI);  // false