Address Lookup Table

Overview

Solana transactions declare the accounts that instructions can read or write. Complex applications can need many program, token, market, and user accounts. Repeating every 32-byte address in the transaction message consumes substantial space. An ALT stores addresses on-chain. A versioned transaction includes the table address and lists compact indexes for the required entries. Validators load the corresponding addresses when processing the message.

Tables must be created, extended, and activated according to network rules. Recently added addresses may not be immediately usable in the same slot. An authority can extend or deactivate a table, while closing it involves additional lifecycle constraints. Applications should verify that each index resolves to the intended account before signing. A malicious transaction builder could reference an unexpected address through a lookup table even when the displayed message appears compact. Wallets and hardware signers need reliable expansion for human-readable review. Lookup tables do not reduce account access or execution cost by themselves; they reduce transaction-message size. They also introduce an on-chain dependency that must remain available and correctly indexed.

Developers should monitor table capacity, authority security, deactivation status, and network version compatibility. ALTs are an address-compression tool for Solana transactions, not a general cross-chain address directory.

Applications should avoid placing highly dynamic or untrusted destinations into shared lookup tables without governance. A table controlled by a compromised authority can be extended with malicious addresses, and compact transaction displays may make the change difficult to notice. Immutable or tightly controlled tables, clear naming, and transaction expansion before signing reduce this risk for complex institutional workflows.