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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

Hardfork	Consensus	Change
Frontier - Gray Glacier	Proof of Work	Ethash mining
Merge+	Proof of Stake	Beacon chain validators

Major Opcode Additions

Hardfork	Opcodes	Purpose
Homestead	DELEGATECALL	Execute in caller context
Byzantium	REVERT, STATICCALL	Error handling, view functions
Constantinople	CREATE2, SHL/SHR/SAR	Deterministic addresses, shifts
Istanbul	CHAINID, SELFBALANCE	Chain ID, gas optimization
London	BASEFEE	EIP-1559 base fee
Merge	PREVRANDAO (replaces DIFFICULTY)	PoS randomness
Shanghai	PUSH0	Gas savings
Cancun	TLOAD/TSTORE, MCOPY, BLOBHASH	Transient storage, blobs

Feature Timeline

Feature	Hardfork	EIP
DELEGATECALL	Homestead	EIP-7
REVERT	Byzantium	EIP-140
STATICCALL	Byzantium	EIP-214
CREATE2	Constantinople	EIP-1014
CHAINID	Istanbul	EIP-1344
Access Lists	Berlin	EIP-2930
EIP-1559	London	EIP-1559
Proof of Stake	Merge	EIP-3675
PUSH0	Shanghai	EIP-3855
Blob Transactions	Cancun	EIP-4844
Transient Storage	Cancun	EIP-1153
BLS Precompiles	Prague	EIP-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

features.mdx - Feature detection methods
comparisons.mdx - Version comparison
index.mdx - Main documentation

Documentation Index

Try it Live

​Hardfork Timeline

​Overview

​Hardfork Constants

​Complete Timeline

​FRONTIER (July 2015)

​HOMESTEAD (March 2016)

​DAO (July 2016)

​TANGERINE_WHISTLE (October 2016)

​SPURIOUS_DRAGON (November 2016)

​BYZANTIUM (October 2017)

​CONSTANTINOPLE (February 2019)

​PETERSBURG (February 2019)

​ISTANBUL (December 2019)

​MUIR_GLACIER (January 2020)

​BERLIN (April 2021)

​LONDON (August 2021)

​ARROW_GLACIER (December 2021)

​GRAY_GLACIER (June 2022)

​MERGE (September 2022)

​SHANGHAI (April 2023)

​CANCUN (March 2024)

​PRAGUE (May 2025)

​OSAKA (TBD)

​Summary Tables

​Consensus Changes

​Major Opcode Additions

​Feature Timeline

​Usage

​Related

Hardfork Timeline

Overview

Hardfork Constants

Complete Timeline

FRONTIER (July 2015)

HOMESTEAD (March 2016)

DAO (July 2016)

TANGERINE_WHISTLE (October 2016)

SPURIOUS_DRAGON (November 2016)

BYZANTIUM (October 2017)

CONSTANTINOPLE (February 2019)

PETERSBURG (February 2019)

ISTANBUL (December 2019)

MUIR_GLACIER (January 2020)

BERLIN (April 2021)

LONDON (August 2021)

ARROW_GLACIER (December 2021)

GRAY_GLACIER (June 2022)

MERGE (September 2022)

SHANGHAI (April 2023)

CANCUN (March 2024)

PRAGUE (May 2025)

OSAKA (TBD)

Summary Tables

Consensus Changes

Major Opcode Additions

Feature Timeline

Usage

Related