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Account constraints provide automatic validation and security checks.

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Initialization constraints

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init

Initialize a new account. 
#[account(init, payer = user, space = 8 + 8)]
pub data: Account<'info, Data>
Required with:
  • payer - Who pays for the account
  • space - Account size in bytes

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init_if_needed

Initialize only if the account doesn’t exist. 
#[account(init_if_needed, payer = user, space = 8 + 8)]
pub data: Account<'info, Data>

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Mutability constraints

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mut

Mark account as mutable. 
#[account(mut)]
pub data: Account<'info, Data>

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Validation constraints

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has_one

Validate an account field matches another account. 
#[account(has_one = authority)]
pub data: Account<'info, Data>
Checks: data.authority == authority.key()

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constraint

Custom validation expression. 
#[account(constraint = data.value < 100)]
pub data: Account<'info, Data>

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PDA constraints

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seeds

Validate PDA derivation. 
#[account(
    seeds = [b"data", user.key().as_ref()],
    bump
)]
pub data: Account<'info, Data>

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bump

Specify bump seed for PDA. 
#[account(seeds = [b"data"], bump = data.bump)]
pub data: Account<'info, Data>

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Closing constraints

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close

Close account and return lamports. 
#[account(mut, close = authority)]
pub data: Account<'info, Data>

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Reallocation constraints

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realloc

Change account size. 
#[account(
    mut,
    realloc = 8 + new_size,
    realloc::payer = user,
    realloc::zero = true
)]
pub data: Account<'info, Data>

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Token constraints

For SPL token accounts: 
#[account(
    init,
    payer = user,
    token::mint = mint,
    token::authority = authority
)]
pub token_account: Account<'info, TokenAccount>
See SPL Integrations for token constraint details.

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Complete reference

See the source code for all constraints.

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