Master Edition

What it is

A Master Edition account turns a regular Metaplex metadata NFT into a “master” that can mint numbered prints (editions) of itself — like an artist’s signed master from which a limited run is printed. Its existence is also what makes a token a true non-fungible 1-of-1 (supply capped at 1, decimals 0).

Why it exists

NFT use cases need both unique 1-of-1s and limited editions (“100 prints of this artwork”). The Master Edition account both certifies non-fungibility and tracks how many editions have been printed against an optional cap. A mint with a Master Edition is provably an NFT, not a divisible token.

Byte layout

MasterEditionV2 is Borsh-encoded. Its account is a PDA of the mint with the seed suffix "edition".

Total: 18 bytes when max_supply is set, 10 bytes when it’s None (unlimited prints).

Where you see it

Every 1-of-1 NFT (where max_supply = Some(0) — no prints allowed) and every limited-edition drop (where max_supply = Some(N)). Marketplaces read the Master Edition to confirm an asset is a genuine NFT and to show “edition X of N.”

Common gotchas

• max_supply = Some(0) means a pure 1-of-1. Zero prints allowed — the master itself is the only copy. Some(100) allows 100 numbered prints; None allows unlimited.
• supply counts prints, not the master. It starts at 0 and increments as editions are printed via EditionMarker tracking.
• It’s a PDA seeded with "edition". Address = findProgramAddress(["metadata", program_id, mint, "edition"]). The same derivation locates a print edition’s Edition account.
• Borsh option (1-byte tag), not SPL COption. max_supply is Option<u64> — a single 0 byte for None. Don’t apply the 4-byte COption convention here.