Borsh Structs

Borsh structs are the workhorse for Solana account bodies. Design them for stable field order, explicit sizing, and forward-compatible versioning.

Recipe

#[derive(BorshSerialize, BorshDeserialize)]
pub struct User { pub authority: Pubkey, pub points: u64 }

When to reach for this:

• Defining new account types.
• Calculating rent space.
• Planning schema upgrades.

Working Example

#[derive(BorshSerialize, BorshDeserialize)]
pub struct User {
    pub authority: Pubkey,
    pub points: u64,
    pub bump: u8,
}
 
impl User {
    pub const LEN: usize = 32 + 8 + 1;
}

What this demonstrates:

• Field order is serialization order.
• LEN matches sum of fields.
• Bump stored for PDA signing.

Deep Dive

Sizing

Pubkey 32 + u64 8 + u8 1 = 41 bytes body.

Versioning

Append fields; migrate old accounts.

Rust Notes

// Option<Pubkey>: 1 + 32 bytes

Gotchas

• Reorder fields - Breaks all accounts. Fix: Only append new fields.
• String without max - Unbounded rent. Fix: Cap length or use fixed array.
• Enum in account - Variant changes risky. Fix: Prefer u8 tag + struct.
• LEN wrong - Runtime failures. Fix: Test serialize len.
• Missing padding awareness - Rare in Borsh - unlike C layouts. Fix: Borsh is packed sequentially.

Alternatives

FAQs

Related

• Borsh Serialization - Format
• Space Calculation - Rent
• Data Versioning & Migration - Upgrades

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. 636f64656775696465732e696f7c6367696f3238367c323032363037