Solana just made its transactions a lot roomier. The network’s new V1 transaction format has gone live on testnet, tripling the maximum serialized transaction size from 1,232 bytes to 4,096 bytes. That 3.3x expansion removes a bottleneck that has forced developers to use awkward workarounds for years.
The upgrade, defined by two protocol proposals called SIMD-0296 and SIMD-0385, is designed to natively support zero-knowledge proofs, large multisig transactions, confidential transfers, and BLS signatures, all within a single transaction. Mainnet activation is confirmed for September 9, 2026.
What the V1 format actually changes
Solana’s legacy transaction format capped payloads at 1,232 bytes. That’s fine for a simple token swap, but it’s painfully tight for anything involving cryptographic proofs or transactions requiring dozens of signers. Zero-knowledge proofs often produce payloads that simply couldn’t fit. Developers had to split operations across multiple transactions or build custom compression schemes.
The V1 format raises the ceiling to 4,096 bytes. SIMD-0296 handles the size limit increase itself, while SIMD-0385 defines the new v1 message format, which uses a 0x81 version byte and a config mask. One notable trade-off: Address Lookup Table (ALT) support has been removed in the new format. Legacy transactions remain fully supported, so nothing breaks for existing applications.
