Programming Model

AccountLoader (Anchor)

An Anchor account type that provides zero-copy access to large account data without deserializing the entire account upfront. AccountLoader wraps the raw account data and provides load() and load_mut() methods to access the data as a typed reference. It is used with #[account(zero_copy)] structs and is preferred over Account<T> when accounts exceed ~1KB, as it significantly reduces compute unit consumption.

IDaccount-loader

Plain meaning

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An Anchor account type that provides zero-copy access to large account data without deserializing the entire account upfront. AccountLoader wraps the raw account data and provides load() and load_mut() methods to access the data as a typed reference. It is used with #[account(zero_copy)] structs and is preferred over Account<T> when accounts exceed ~1KB, as it significantly reduces compute unit consumption.

Mental model

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Think of it as one of the core moving pieces your program reads, writes, or invokes at runtime.

Technical context

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Accounts, instructions, PDAs, transactions, and execution flow.

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AccountLoader (Anchor) (account-loader)
Category: Programming Model
Definition: An Anchor account type that provides zero-copy access to large account data without deserializing the entire account upfront. AccountLoader wraps the raw account data and provides load() and load_mut() methods to access the data as a typed reference. It is used with #[account(zero_copy)] structs and is preferred over Account<T> when accounts exceed ~1KB, as it significantly reduces compute unit consumption.
Related: Zero-Copy Deserialization, Anchor Framework, Account Data
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Concept graph

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Branch

Zero-Copy Deserialization

A technique for accessing on-chain account data directly from the underlying byte buffer without copying it into a new Rust struct, avoiding heap allocation and reducing compute unit usage. In Anchor, zero-copy is enabled via #[account(zero_copy)] on the account struct, which uses repr(C) layout and the AccountLoader type. Ideal for large accounts (>1KB) where Borsh deserialization would be expensive.

Branch

Anchor Framework

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.

Branch

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Next concepts to explore

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Programming Model

Zero-Copy Deserialization

A technique for accessing on-chain account data directly from the underlying byte buffer without copying it into a new Rust struct, avoiding heap allocation and reducing compute unit usage. In Anchor, zero-copy is enabled via #[account(zero_copy)] on the account struct, which uses repr(C) layout and the AccountLoader type. Ideal for large accounts (>1KB) where Borsh deserialization would be expensive.

Developer Tools

Anchor Framework

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.

Programming Model

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Programming Model

Address Lookup Table (ALT)

An on-chain account that stores up to 256 pubkeys, enabling v0 transactions to reference accounts by 1-byte index instead of full 32-byte pubkeys. ALTs dramatically reduce transaction size when interacting with many accounts (e.g., DEX routing). ALTs must be created and populated in advance; entries become active after a slot delay.

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Programming Modelaccount

Account

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.

Programming Modelloader

Loader

A built-in program responsible for deploying, loading, and executing on-chain programs by interpreting their binary encoding. Solana has multiple loaders: the original BPF Loader (deprecated, immutable programs), BPF Loader 2 (deprecated), and the current Upgradeable BPF Loader that supports program upgrades and manages the program/program-data account split.

Programming Modelaccount-data

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Related terms

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Programming Modelzero-copy-deserialization

Zero-Copy Deserialization

A technique for accessing on-chain account data directly from the underlying byte buffer without copying it into a new Rust struct, avoiding heap allocation and reducing compute unit usage. In Anchor, zero-copy is enabled via #[account(zero_copy)] on the account struct, which uses repr(C) layout and the AccountLoader type. Ideal for large accounts (>1KB) where Borsh deserialization would be expensive.

Developer Toolsanchor

Anchor Framework

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.

Programming Modelaccount-data

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

More in category

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Programming Model

Account

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.

Programming Model

Program

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).

Programming Model

Instruction

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.

Programming Model

Transaction

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.