Token Metadata

MetadataV1 account — links a mint to its name, symbol, URI, royalties, creators, and optional collection. The foundation of every Solana NFT.

Metaplex Token Metadata 607 bytes

Sample: Mad Lads

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What it is

A Metaplex Token Metadata account attaches a name, symbol, image URI, and creator royalties to an SPL Mint — the foundation of every Solana NFT and most fungible-with-metadata tokens.

Why it exists

SPL Mint accounts are just numbers: supply, decimals, authorities. For NFTs you need a name, a picture, creators to pay royalties to, and a way to point to off-chain JSON. Metaplex’s Token Metadata program stores that on-chain as a separate account derived from the mint via a fixed PDA: ["metadata", program_id, mint_pubkey].

Byte layout

The 607-byte MetadataV1 layout is dominated by three padded variable-length strings and several Option fields. Padding is zero-byte filled to fixed maxima.

Offset	Length	Field	Type	Notes
0	1	`key`	`u8` enum	`4` = MetadataV1.
1	32	`update_authority`	`Pubkey`	Can update fields while `is_mutable`.
33	32	`mint`	`Pubkey`	The SPL Mint this metadata describes.
65	36	`name`	padded string	4-byte length + up to 32 bytes UTF-8.
101	14	`symbol`	padded string	4-byte length + up to 10 bytes UTF-8.
115	204	`uri`	padded string	4-byte length + up to 200 bytes UTF-8. Points at off-chain JSON.
319	2	`seller_fee_basis_points`	`u16` LE	Royalty in basis points (500 = 5%).
321	var	`creators`	`Option<Vec<Creator>>`	1-byte Option tag + 4-byte length + 34-byte Creator entries.
…	1	`primary_sale_happened`	`bool`
…	1	`is_mutable`	`bool`	If false, fields are frozen forever.
…	2	`edition_nonce`	`Option<u8>`	1-byte Option tag + 1-byte nonce.
…	2	`token_standard`	`Option<u8>` enum	NonFungible, Fungible, ProgrammableNonFungible, etc.
…	var	`collection`	`Option<Collection>`	Linked collection mint.
…	var	`uses`	`Option<Uses>`	Burn/multi/single use tracking.

Total: 607 bytes (padded to fixed size; variable fields fill to maximum).

Where you see it

Wallets and marketplaces resolve any NFT mint to its Token Metadata account to render the name and image. Most fungible tokens use Metaplex too (USDC’s logo and name come from a Metadata account). Token-2022 introduced an alternative inline metadata extension that avoids the separate account, but Metaplex remains dominant for NFTs.

Common gotchas

Padded strings, not Borsh-style. name/symbol/uri are length-prefixed but always padded to maximum size on-chain. The trailing zero bytes are part of the layout.
is_mutable: false is permanent. Once set, no field can be changed. Many collections immutabilize after mint-out to prove provenance.
Metaplex uses Borsh Option (1-byte tag), not SPL’s COption (4-byte tag). The two encodings live side-by-side on Solana — easy source of off-by-3 bugs.
Royalties are advisory. On-chain seller_fee_basis_points doesn’t force marketplaces to pay — pNFTs (Programmable NFTs) added enforcement via a separate ruleset.

Sources

Metaplex Metadata struct (mpl-token-metadata)