Standard / EIP·EVM
ERC-404 — Fractional NFTs (community standard)
Unofficial community standard — NOT an accepted EIP. Hybrid ERC-20 / ERC-721 token where each whole unit is also an NFT: transferring a fractional balance burns/mints the underlying NFT. Multiple competing implementations exist (original ERC-404 by Pandora, DN-404 by Solady, ERC-404a).
- 01fractional NFT collections with native liquidity
- 02PFP projects that want DEX-tradable units
- 03experimental hybrid fungible/non-fungible markets
- 04memecoins with collectible artwork tied to whole units
ERC-404 has no canonical EIP. The three implementations to choose between are: (1) Pandora Labs' original `ERC404` (`github.com/Pandora-Labs-Org/erc404`) — the first version, deployed by the Pandora token; (2) `DN404` from Vectorized/Solady (`solady/src/tokens/DN404.sol` + `DN404Mirror.sol`) — splits the ERC-20 ledger and ERC-721 'mirror' into two contracts to be fully spec-compliant with both standards (recommended for new projects); (3) ERC-404a, a later iteration. Pick DN-404 for production unless you have a specific reason — it avoids the spec violations of the original (which fails ERC-721 `Transfer` event semantics in many flows). Whichever you choose, expose the standard ERC-20 interface on the main contract and an ERC-721 interface on either the same contract (legacy ERC-404) or a paired mirror contract (DN-404). Whitelist DEX pools and bridges from NFT mint/burn-on-transfer logic to avoid gas blowups.
- ⚑Original ERC-404 violates parts of both ERC-20 and ERC-721 specs (e.g. unexpected NFT mint/burn events on plain transfers). Many indexers, marketplaces, and bridges break or display incorrect data.
- ⚑Every fractional transfer that crosses a whole-unit boundary mints or burns NFTs — gas is unpredictable and can be 10–50x a normal ERC-20 transfer.
- ⚑Holders sitting in a DEX pool effectively give up their NFT identities — most implementations require manual whitelisting of router/pool addresses to skip NFT mechanics.
- ⚑There is no audit-blessed 'reference' — DN-404 is the closest to spec-correct, but it is itself unaudited at the EIP level. Treat any ERC-404 contract as experimental.
- ⚑Cross-chain support is essentially nonexistent; bridges will not preserve the NFT/fungible coupling.
- ⚑Marketplaces (OpenSea, Blur) have inconsistent rendering — some collections appear with phantom mints/burns in their history.