Type reference

Hexadecimal quantities, byte strings, addresses, hashes, block selectors, and transaction call objects used by MegaETH JSON-RPC.

This page defines wire types shared by MegaETH JSON-RPC methods. Method pages remain self-contained and specify the types accepted in each position.

Core wire types

Quantity

A Quantity is a non-negative integer encoded as a 0x-prefixed hexadecimal string. It uses the shortest representation, so leading zeroes are not allowed except in 0x0.

Valid	Invalid
0x0	0
0x1	0x01
0x5208	21000

Data

Data is an arbitrary byte sequence encoded as a 0x-prefixed hexadecimal string. It contains exactly two hexadecimal digits per byte and may be empty.

Valid	Invalid
0x	0
0x12	0x1
0xdeadbeef	deadbeef

Address

An Address is a 20-byte value encoded as 0x followed by 40 hexadecimal digits. The wire format accepts upper- or lowercase hexadecimal digits.

Example: 0x0000000000000000000000000000000000000000.

Hash32

A Hash32 is a 32-byte hash encoded as 0x followed by 64 hexadecimal digits. Block hashes, transaction hashes, and trie roots use this representation.

Bytes32

Bytes32 has the same wire width as Hash32 but represents a fixed-width value rather than necessarily a hash. Storage keys and proof values commonly use this representation.

Block selectors

Methods that read block or state data may accept a block number encoded as Quantity or one of these tags:

Tag	Meaning on MegaETH
earliest	The genesis block.
latest	The latest streaming state, including committed mini-blocks.
pending	The latest streaming state.
safe	The latest safe EVM block known to the node.
finalized	The latest finalized EVM block known to the node.

Some methods also accept an EIP-1898 block selector object containing blockHash or blockNumber. Check the method page before using the object form because support is method-specific.

Transaction call object

Simulation methods such as eth_call, eth_estimateGas, and eth_createAccessList accept a transaction call object. Common fields include:

Field	Type	Description
from	Address	Simulated sender.
to	Address or null	Recipient, or null for contract creation.
gas	Quantity	Gas limit supplied to the simulation.
gasPrice	Quantity	Legacy gas price.
maxFeePerGas	Quantity	EIP-1559 maximum fee.
maxPriorityFeePerGas	Quantity	EIP-1559 priority fee.
value	Quantity	Value transferred in wei.
input or data	Data	Calldata or contract creation bytecode.
nonce	Quantity	Sender nonce when the method supports it.
accessList	array	EIP-2930 access list.

Do not combine gasPrice with EIP-1559 fee fields. Use the relevant method page for accepted fields and defaults.

Common validation mistakes

Mistake	Wrong	Correct
Decimal quantity	21000	"0x5208"
Leading zeroes	"0x0001"	"0x1"
Odd-length data	"0x123"	"0x0123"
Short address	"0x1234"	A full 20-byte address
Mixed log selector modes	blockHash with fromBlock	Use one selector mode
Mixed fee models	gasPrice with maxFeePerGas	Use one fee model

Source

• EIP-1474: Value encoding