Transaction size

Legacy and v0 transactions are limited to 1,232 bytes — the IPv6 minimum packet size minus headers. Signatures and 32-byte account keys use most of it; lookup tables shrink accounts to one byte each.

Signatures

Account keys in the messageincl. signers, programs

Format

Instruction 1: accounts

Instruction 1: data

bytes

Instruction 2: accounts

Instruction 2: data

bytes

Instruction 3: accounts

Instruction 3: data

bytes

The first two rows are SetComputeUnitLimit (5 bytes) and SetComputeUnitPrice (9 bytes).

Serialized sizelimit 1,232 bytes

369bytes

Signatures65B

Header3B

Account keys193B

Blockhash32B

Instructions76B

Lookup tables0B

863 bytes left. Each length prefix is a compact-u16 (1 byte below 128).

Wire format: signatures (compact-u16 count + 64 bytes each), message header, account keys, recent blockhash, instructions, and in v0 the lookup-table section. Limit: SIMD-0296, SIMD-0385.

FAQ

What is the Solana transaction size limit?

1,232 bytes for legacy and v0 transactions. SIMD-0296 and the v1 transaction format (SIMD-0385) specify 4,096 bytes for the new format; legacy and v0 keep 1,232.

How do address lookup tables save space?

In a v0 transaction an account stored in a lookup table is referenced by a one-byte index instead of its 32-byte key; each table costs 32 bytes for its own address plus the index lists.

Does a larger transaction pay a higher fee?

Not directly: the base fee is per signature and the priority fee per compute unit. Size limits what fits, not what it costs.

“Transaction too large”Airdrop cost