Glossary
Address Lookup Table (ALT)
A Solana feature that lets transactions reference accounts by an index into a pre-stored on-chain table — used to fit complex transactions under the 1232-byte size limit.
Solana transactions are capped at 1232 bytes. Each referenced account costs 32 bytes; a transaction touching many accounts can hit the limit. Address Lookup Tables solve this: a transaction can reference accounts via a 1-byte index into an on-chain table that holds up to 256 addresses.
ALTs are critical for complex DeFi transactions on Solana — Jupiter aggregator routes, multi-hop swaps, and CPI-heavy operations regularly touch dozens of accounts. Building an ALT properly is a non-trivial part of integration work on Solana.