Solana's new v1 transaction format became active on mainnet on September 15 at epoch 1035, according to the Solana Foundation's upgrade page. It raises the transaction-size ceiling from 1,232 to 4,096 bytes.
The extra capacity gives developers room for larger multisignature operations, cryptographic proofs and batches that previously could not fit into one transaction. It does not mean every existing transaction becomes larger or every application automatically gets faster.
Existing formats keep working
Legacy and v0 transactions remain supported. Applications need the new v1 format to use the expanded space, and wallets must support that format before signing it.
Infrastructure operators face a separate compatibility task. The Foundation says transaction readers must support version 1, while indexers must read resource limits from the new transaction configuration. Applications sending v1 transactions must explicitly set compute and loaded-data limits.
For users, the useful distinction is between a live network feature and support in a particular wallet or app. The larger format is available, but using it depends on the software handling the transaction.