Pushdata Opcodes

The Pushdata opcodes each use the value of the data item in the script to determine the length of the data item to push onto the stack.

Opcodes 1-75 (0x01 – 0x4B)

Opcodes 1-75 simply push their value of bytes of data onto the stack.

Examples:

0x08 <8 byte data item> – would leave the 8 byte data item on the stack.

0x20 <32 byte data item> – would leave the 32 byte data item on the stack

OP_PUSHDATA1 (76 or 0x4C)

OP_PUSHDATA1 takes the next 1 byte as the number of bytes to push onto the stack. It can be used to push data items of length from 1 to 255 bytes onto the stack, however is typically only used for data items over 75 bytes in size.

Examples: 0x4C 0x64 <100 byte data item> – would leave the 100 byte data item on the stack

0x4C 0xFF <255 byte data item> – would leave the 255 byte data item on the stack

OP_PUSHDATA2 (77 or 0x4D)

OP_PUSHDATA2 takes the next 2 bytes as the number of bytes to push onto the stack. It can be used to push data items of length from 256 to 65,535 bytes onto the stack.

Examples: 0x4D 0x0100 <256 byte data item> – would leave the 256 byte data item on the stack

0x4D 0xFFFF <65,535 byte data item> – would leave the 65,535 byte data item on the stack

OP_PUSHDATA4 (78 or 0x4E)

OP_PUSHDATA4 takes the next 4 bytes as the number of bytes to push onto the stack. It can be used to push data items of length from 65,536B up to ‭4,294,967,295‬B onto the stack.

Examples: 0x4E 0x00010000 <65,536 byte data item> – would leave the 65,536 byte data item on the stack

0x4E 0xFFFFFFFF <‭4,294,967,295‬ byte data item> – would leave the ‭4,294,967,295‬ byte data item on the stack

OP_PUSHDATA4 is the largest Pushdata opcode in Bitcoin script limiting the size of individual data items in script to ‭4,294,967,295‬B. Once data items are on the stack it is possible to use OP_CAT to join them together, creating larger items for purposes such as file hash verifications and more.