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Elementary types

Elementary types are atomic—they don't contain other types. These form the building blocks that complex types compose.

Numeric types​

Unsigned integers (uint)​

Unsigned integers range from 8 to 256 bits, in increments of 8:

{ "kind": "uint", "bits": 256 }
{ "kind": "uint", "bits": 8 }

The bits field is required and must be a multiple of 8 between 8 and 256.

Signed integers (int)​

Signed integers use two's complement representation:

{ "kind": "int", "bits": 256 }

Like uint, the bits field must be a multiple of 8 between 8 and 256.

Fixed-point numbers (ufixed, fixed)​

Fixed-point decimals specify both total bits and decimal places:

{ "kind": "ufixed", "bits": 128, "places": 18 }
{ "kind": "fixed", "bits": 128, "places": 18 }

Address type​

Addresses represent 20-byte Ethereum addresses:

{ "kind": "address" }

In Solidity, address payable is a distinct type but uses the same representation—the distinction is semantic rather than structural.

Boolean type​

Booleans represent true/false values:

{ "kind": "bool" }

In the EVM, booleans occupy a full 32-byte word where 0 is false and any non-zero value is true.

Byte types​

Fixed-size bytes (bytes)​

Fixed-size byte arrays range from 1 to 32 bytes:

{ "kind": "bytes", "size": 32 }
{ "kind": "bytes", "size": 4 }

The size field is required for fixed-size bytes.

Dynamic bytes (bytes)​

Dynamic byte arrays have no size limit:

{ "kind": "bytes" }

When size is omitted, the type represents dynamically-sized bytes.

String type​

Strings represent UTF-8 encoded text:

{ "kind": "string" }

Strings are dynamically sized. Languages that treat strings as character arrays may choose to represent them as array types instead.

Enum type​

Enums represent a fixed set of named values:

{
  "kind": "enum",
  "definition": {
    "name": "Status"
  },
  "values": ["Pending", "Active", "Completed"]
}

The values field lists all possible values in order. The underlying representation is typically a uint8 (or larger if needed).

User-defined types with definitions​

Some elementary types (particularly enums) are defined in source code. These include a definition field:

{
  "kind": "enum",
  "definition": {
    "name": "OrderStatus",
    "source": {
      "id": 42,
      "range": {
        "start": { "line": 10, "column": 0 },
        "end": { "line": 15, "column": 1 }
      }
    }
  },
  "values": ["Created", "Filled", "Cancelled"]
}

The definition field can include:

  • name: The identifier used in source code
  • source: A reference to where the type is defined

Learn more​

For complete schema definitions and all available fields, see the elementary types specification.