GB / OPCODES
A POCKET-SIZED CPU. EVERY INSTRUCTION.

Game Boy Opcodes.

The instruction set, at your fingertips. Explore the Sharp LR35902
one byte at a time.

501 instructions8-bit architecture2 opcode tables
BASE OPCODESLoading instructions…
Select an instruction to inspect itHex row + column = opcode
01

Find your instruction

Search by mnemonic, operand, or hexadecimal byte.

02

Follow the colors

Instruction families make patterns in the CPU visible.

03

Look under the hood

Select a cell for timing, flags, and the source data.

A QUICK FIELD GUIDE

Reading the opcode map

The row gives the high nibble and the column gives the low nibble. Row 3 + column E is opcode 0x3E. CB instructions start with the prefix byte 0xCB.

Inside each cell

The instruction is followed by its byte length and timing. T-cycles are CPU clock cycles; one M-cycle equals four T-cycles. For conditional instructions, two timings mean taken / not taken.

CPU flags: Z · N · H · C

Zero, subtract, half carry, and carry. — means unchanged, 0 means cleared, 1 means set, and a letter means the result determines the flag.

Operands

d8 / d16 = immediate data; a8 / a16 = address; r8 = signed relative offset. Parentheses indicate a memory operand.

Keyboard shortcuts

/ focus search · Esc clear search or close help.
Focus a map cell and use arrow keys to move through the table.

This viewer displays opcodes.json as supplied, including its group classifications and timings. Empty addresses are absent from the dataset. It is a data explorer, not a CPU simulator.