Interface Definition Language—a JSON specification that describes a program's instructions, accounts, types, and error codes. Anchor auto-generates the IDL from the program source code. Client libraries (TypeScript, Python) use the IDL to serialize/deserialize instruction data and accounts, enabling type-safe interaction without manual encoding.
Start with the shortest useful explanation before going deeper.
Interface Definition Language—a JSON specification that describes a program's instructions, accounts, types, and error codes. Anchor auto-generates the IDL from the program source code. Client libraries (TypeScript, Python) use the IDL to serialize/deserialize instruction data and accounts, enabling type-safe interaction without manual encoding.
Use the quick analogy first so the term is easier to reason about when you meet it in code, docs, or prompts.
Think of it as one of the core moving pieces your program reads, writes, or invokes at runtime.
Place the term inside its Solana layer so the definition is easier to reason about.
Accounts, instructions, PDAs, transactions, and execution flow.
Turn the term from vocabulary into something operational for product and engineering work.
Most useful when you are moving through Anchor Builder Path and need grounded vocabulary inside a real build flow.
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IDL (Interface Definition Language) (idl) Category: Programming Model Definition: Interface Definition Language—a JSON specification that describes a program's instructions, accounts, types, and error codes. Anchor auto-generates the IDL from the program source code. Client libraries (TypeScript, Python) use the IDL to serialize/deserialize instruction data and accounts, enabling type-safe interaction without manual encoding. Aliases: IDL Related: Anchor Framework, Program
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The most popular framework for building Solana programs in Rust. Anchor provides macros (#[program], #[account], #[derive(Accounts)]) that auto-generate boilerplate for account validation, serialization, discriminators, and error handling. It includes a CLI (anchor init/build/test/deploy), IDL generation, and TypeScript client generation. Reduces program code by ~80% compared to native development.
Executable code deployed on-chain, equivalent to a smart contract on other blockchains. Programs are stateless—they store no data themselves but read/write data in separate accounts they own. Programs are compiled to SBF bytecode and loaded via the BPF Loader. Every program has a unique Program ID (its account's public key).
These are the next concepts worth opening if you want this term to make more sense inside a real Solana workflow.
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The most popular framework for building Solana programs in Rust. Anchor provides macros (#[program], #[account], #[derive(Accounts)]) that auto-generate boilerplate for account validation, serialization, discriminators, and error handling. It includes a CLI (anchor init/build/test/deploy), IDL generation, and TypeScript client generation. Reduces program code by ~80% compared to native development.
Executable code deployed on-chain, equivalent to a smart contract on other blockchains. Programs are stateless—they store no data themselves but read/write data in separate accounts they own. Programs are compiled to SBF bytecode and loaded via the BPF Loader. Every program has a unique Program ID (its account's public key).
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The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.
Executable code deployed on-chain, equivalent to a smart contract on other blockchains. Programs are stateless—they store no data themselves but read/write data in separate accounts they own. Programs are compiled to SBF bytecode and loaded via the BPF Loader. Every program has a unique Program ID (its account's public key).
A single operation within a transaction that invokes a program. An instruction specifies: (1) the program ID to call, (2) an array of account metas (pubkey, is_signer, is_writable), and (3) an opaque data byte array. Programs decode the instruction data to determine which operation to perform.
An atomic unit of execution containing one or more instructions, a recent blockhash, and one or more signatures. All instructions in a transaction execute sequentially and atomically—if any instruction fails, the entire transaction reverts. Transactions have a 1,232-byte size limit (matching IPv6 MTU) and a default 200,000 CU budget.