The Accounts Struct

Q: What Anchor version does this site use?

0.32.1 for anchor-lang, Anchor CLI, and examples in this section.

Q: Do I need Solana CLI alongside Anchor?

Yes. Solana CLI 3.0.10 handles keypairs, airdrops, and solana program inspection.

Q: Where does the IDL live after build?

target/idl/.json in your workspace.

Q: How do I test without devnet?

Use anchor test with Surfpool 0.12.0 or LiteSVM 0.6.x in CI.

Q: What is the 8-byte prefix on account data?

Anchor account discriminator; do not strip it when sizing space.

Every instruction declares an accounts struct with #[derive(Accounts)]. Anchor runs constraints before your handler executes, enforcing ownership, mutability, and relationships fail-closed.

Recipe

#[derive(Accounts)]
pub struct Transfer<'info> {
    #[account(mut)]
    pub from: Signer<'info>,
    #[account(mut, constraint = to.owner == from.key())]
    pub to: Account<'info, TokenAccount>,
    pub token_program: Program<'info, Token>,
}

When to reach for this: You design any instruction that touches on-chain accounts.

Working Example

#[derive(Accounts)]
pub struct UpdateMetadata<'info> {
    #[account(
        mut,
        seeds = [b"meta", authority.key().as_ref()],
        bump = metadata.bump,
        has_one = authority,
    )]
    pub metadata: Account<'info, Metadata>,
    pub authority: Signer<'info>,
}
 
#[account]
pub struct Metadata {
    pub authority: Pubkey,
    pub bump: u8,
    pub uri: String,
}

What this demonstrates:

Field types (Signer, Account<T>, Program<T>) imply base checks
Attribute constraints add seeds, init, has_one, and custom expressions
bumps map is available in handlers for stored canonical bumps
Validation order matters for init and CPI safety

Deep Dive

Common Account Types

Type	Validates
`Signer<'info>`	Account signed the transaction
`Account<'info, T>`	Owner is program, deserializes as `T`
`Program<'info, T>`	Address matches program ID for `T`
`SystemAccount<'info>`	Owned by system program
`UncheckedAccount<'info>`	No automatic checks (use carefully)

Constraint Categories

Mutability - mut for writable accounts.
Ownership - owner, has_one, token constraints.
Address - address = expr, seeds/bump for PDAs.
Lifecycle - init, init_if_needed, close.

Gotchas

UncheckedAccount without constraints - Any account passes validation. Fix: Add address, owner, or constraint.
Missing mut on writable account - Runtime failure on write. Fix: Mark every written account mut.
has_one on wrong field - Relationship not enforced. Fix: Match field name to struct field on account data.
Init without payer - Account creation fails. Fix: Set payer = signer and include system program.
Trusting client-provided PDAs - Wrong seeds drain funds. Fix: Always use seeds + bump constraints.

Alternatives

Alternative	Use When	Don't Use When
Manual validation in handler	Dynamic checks hard to express	Prefer declarative constraints for static rules
remaining_accounts	Variable account sets	Fixed layout known at compile time
AccountLoader for zero-copy	Large accounts	Small structs with Borsh

FAQs

What Anchor version does this site use?

0.32.1 for anchor-lang, Anchor CLI, and examples in this section.

Do I need Solana CLI alongside Anchor?

Yes. Solana CLI 3.0.10 handles keypairs, airdrops, and solana program inspection.

Where does the IDL live after build?

target/idl/<program>.json in your workspace.

Can I mix UncheckedAccount with Signer?

Yes, but every unchecked field needs explicit constraints or handler checks.

How do I test without devnet?

Use anchor test with Surfpool 0.12.0 or LiteSVM 0.6.x in CI.

What is the 8-byte prefix on account data?

Anchor account discriminator; do not strip it when sizing space.

Should I commit generated IDL?

Yes, or publish on-chain IDL so clients have a canonical source.

How do I debug constraint failures?

Run with logs; Anchor prints constraint name and account index.

Does Anchor work on Agave 4.1.1?

Yes. This stack targets Agave validators with Solana CLI 3.0.10.

What should I read next in this section?

See sibling articles linked in Related for deeper accounts struct topics.

Account Types - type reference
The #[account] Constraints - constraint catalog
Account Validation Order - check sequence

Stack versions: This page was written for Agave 4.1.1, Solana CLI 3.0.10, Anchor 0.32.1, anchor-lang 0.32.1, Rust 1.91.1, @solana/kit 7.0.0, Surfpool 0.12.0, and LiteSVM 0.6.x.

Recipe

#[derive(Accounts)]
pub struct Transfer<'info> {
    #[account(mut)]
    pub from: Signer<'info>,
    #[account(mut, constraint = to.owner == from.key())]
    pub to: Account<'info, TokenAccount>,
    pub token_program: Program<'info, Token>,
}

When to reach for this: You design any instruction that touches on-chain accounts.

Working Example

#[derive(Accounts)]
pub struct UpdateMetadata<'info> {
    #[account(
        mut,
        seeds = [b"meta", authority.key().as_ref()],
        bump = metadata.bump,
        has_one = authority,
    )]
    pub metadata: Account<'info, Metadata>,
    pub authority: Signer<'info>,
}
 
#[account]
pub struct Metadata {
    pub authority: Pubkey,
    pub bump: u8,
    pub uri: String,
}

What this demonstrates:

Field types (Signer, Account<T>, Program<T>) imply base checks
Attribute constraints add seeds, init, has_one, and custom expressions
bumps map is available in handlers for stored canonical bumps
Validation order matters for init and CPI safety

Deep Dive

Common Account Types

Type	Validates
`Signer<'info>`	Account signed the transaction
`Account<'info, T>`	Owner is program, deserializes as `T`
`Program<'info, T>`	Address matches program ID for `T`
`SystemAccount<'info>`	Owned by system program
`UncheckedAccount<'info>`	No automatic checks (use carefully)

Constraint Categories

Mutability - mut for writable accounts.
Ownership - owner, has_one, token constraints.
Address - address = expr, seeds/bump for PDAs.
Lifecycle - init, init_if_needed, close.

Gotchas

UncheckedAccount without constraints - Any account passes validation. Fix: Add address, owner, or constraint.
Missing mut on writable account - Runtime failure on write. Fix: Mark every written account mut.
has_one on wrong field - Relationship not enforced. Fix: Match field name to struct field on account data.
Init without payer - Account creation fails. Fix: Set payer = signer and include system program.
Trusting client-provided PDAs - Wrong seeds drain funds. Fix: Always use seeds + bump constraints.

Alternatives

Alternative	Use When	Don't Use When
Manual validation in handler	Dynamic checks hard to express	Prefer declarative constraints for static rules
remaining_accounts	Variable account sets	Fixed layout known at compile time
AccountLoader for zero-copy	Large accounts	Small structs with Borsh

FAQs

What Anchor version does this site use?

0.32.1 for anchor-lang, Anchor CLI, and examples in this section.

Do I need Solana CLI alongside Anchor?

Yes. Solana CLI 3.0.10 handles keypairs, airdrops, and solana program inspection.

Where does the IDL live after build?

target/idl/<program>.json in your workspace.

Can I mix UncheckedAccount with Signer?

Yes, but every unchecked field needs explicit constraints or handler checks.

How do I test without devnet?

Use anchor test with Surfpool 0.12.0 or LiteSVM 0.6.x in CI.

What is the 8-byte prefix on account data?

Anchor account discriminator; do not strip it when sizing space.

Should I commit generated IDL?

Yes, or publish on-chain IDL so clients have a canonical source.

How do I debug constraint failures?

Run with logs; Anchor prints constraint name and account index.

Does Anchor work on Agave 4.1.1?

Yes. This stack targets Agave validators with Solana CLI 3.0.10.

What should I read next in this section?

See sibling articles linked in Related for deeper accounts struct topics.

Account Types - type reference
The #[account] Constraints - constraint catalog
Account Validation Order - check sequence

Stack versions: This page was written for Agave 4.1.1, Solana CLI 3.0.10, Anchor 0.32.1, anchor-lang 0.32.1, Rust 1.91.1, @solana/kit 7.0.0, Surfpool 0.12.0, and LiteSVM 0.6.x.

The Accounts Struct

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The Accounts Struct