Outputs: ScriptPubKey Size

Transaction→ScriptPubKey Size

Structure

Version

4 bytes

Segwit (Optional)

Marker

1 byte

Flag

1 byte

Structure

Input Count

variable

Input Structure

Previous TXID

32 bytes

Output Index

4 bytes

ScriptSig Size

variable

ScriptSig

variable

Sequence

4 bytes

Structure

Output Count

variable

Output Structure

Amount

8 bytes

ScriptPubKey Size

variable

ScriptPubKey

variable

Structure

Witness

variable

Structure

Locktime

4 bytes

Size

variable

Format

Compact Size

Description

The size of the output script.

Example

19

Byte Visualization

Byte 1

The ScriptPubKey size is stored as a variable-length integer (varint) that indicates the length of the following ScriptPubKey field in bytes.

Let's examine a real transaction to understand this better:

Common ScriptPubKey Sizes

Different types of Bitcoin addresses result in different ScriptPubKey sizes:

Script Type	Size (bytes)	Compact Size Value
P2PK	35 or 67	0x23 or 0x43
P2PKH	25	0x19
P2SH	23	0x17
P2WPKH	22	0x16
P2WSH	34	0x22

Note

The most common script type today is P2WPKH (Pay to Witness Public Key Hash), which has a ScriptPubKey size of 22 bytes (0x16).

Variable Integer Encoding

Like other variable-length fields in Bitcoin transactions, the ScriptPubKey size uses varint encoding:

Decimal Range	Hex Range	Bytes Used	Format
0 to 252	0x00 to 0xfc	1	uint8_t
253 to 2¹⁶-1	0xfd to 0xffff	3	0xfd + uint16_t
2¹⁶ to 2³²-1	0x10000 to 0xffffffff	5	0xfe + uint32_t
2³² to 2⁶⁴-1	0x100000000 to 0xffffffffffffffff	9	0xff + uint64_t

Implementation Example

Here's how you might parse a ScriptPubKey size:

python

def parse_scriptpubkey_size(raw_tx: bytes, offset: int = 0) -> tuple[int, int]:
    """
    Parse ScriptPubKey size from raw transaction bytes
    
    Args:
        raw_tx: Raw transaction bytes
        offset: Starting position in bytes
        
    Returns:
        (size, new_offset)
    """
    # Read the varint
    first_byte = raw_tx[offset]
    
    if first_byte < 0xfd:
        size = first_byte
        offset += 1
    elif first_byte == 0xfd:
        size = int.from_bytes(raw_tx[offset+1:offset+3], 'little')
        offset += 3
    elif first_byte == 0xfe:
        size = int.from_bytes(raw_tx[offset+1:offset+5], 'little')
        offset += 5
    else:  # 0xff
        size = int.from_bytes(raw_tx[offset+1:offset+9], 'little')
        offset += 9
        
    return size, offset

Warning

The ScriptPubKey size must accurately reflect the length of the following ScriptPubKey field. If these don't match, the transaction is invalid.

Suggest Edits

Previous: Outputs: Amount
Next: Outputs: ScriptPubKey

Outputs: ScriptPubKey Size

Transaction→ScriptPubKey Size

Structure

Version

4 bytes

Segwit (Optional)

Marker

1 byte

Flag

1 byte

Structure

Input Count

variable

Input Structure

Previous TXID

32 bytes

Output Index

4 bytes

ScriptSig Size

variable

ScriptSig

variable

Sequence

4 bytes

Structure

Output Count

variable

Output Structure

Amount

8 bytes

ScriptPubKey Size

variable

ScriptPubKey

variable

Structure

Witness

variable

Structure

Locktime

4 bytes

Size

variable

Format

Compact Size

Description

The size of the output script.

Example

19

Byte Visualization

Byte 1

The ScriptPubKey size is stored as a variable-length integer (varint) that indicates the length of the following ScriptPubKey field in bytes.

Let's examine a real transaction to understand this better:

Common ScriptPubKey Sizes

Different types of Bitcoin addresses result in different ScriptPubKey sizes:

Script Type	Size (bytes)	Compact Size Value
P2PK	35 or 67	0x23 or 0x43
P2PKH	25	0x19
P2SH	23	0x17
P2WPKH	22	0x16
P2WSH	34	0x22

Note

The most common script type today is P2WPKH (Pay to Witness Public Key Hash), which has a ScriptPubKey size of 22 bytes (0x16).

Variable Integer Encoding

Like other variable-length fields in Bitcoin transactions, the ScriptPubKey size uses varint encoding:

Decimal Range	Hex Range	Bytes Used	Format
0 to 252	0x00 to 0xfc	1	uint8_t
253 to 2¹⁶-1	0xfd to 0xffff	3	0xfd + uint16_t
2¹⁶ to 2³²-1	0x10000 to 0xffffffff	5	0xfe + uint32_t
2³² to 2⁶⁴-1	0x100000000 to 0xffffffffffffffff	9	0xff + uint64_t

Implementation Example

Here's how you might parse a ScriptPubKey size:

python

def parse_scriptpubkey_size(raw_tx: bytes, offset: int = 0) -> tuple[int, int]:
    """
    Parse ScriptPubKey size from raw transaction bytes
    
    Args:
        raw_tx: Raw transaction bytes
        offset: Starting position in bytes
        
    Returns:
        (size, new_offset)
    """
    # Read the varint
    first_byte = raw_tx[offset]
    
    if first_byte < 0xfd:
        size = first_byte
        offset += 1
    elif first_byte == 0xfd:
        size = int.from_bytes(raw_tx[offset+1:offset+3], 'little')
        offset += 3
    elif first_byte == 0xfe:
        size = int.from_bytes(raw_tx[offset+1:offset+5], 'little')
        offset += 5
    else:  # 0xff
        size = int.from_bytes(raw_tx[offset+1:offset+9], 'little')
        offset += 9
        
    return size, offset

Warning

The ScriptPubKey size must accurately reflect the length of the following ScriptPubKey field. If these don't match, the transaction is invalid.

Suggest Edits

Previous: Outputs: Amount
Next: Outputs: ScriptPubKey