Traditional ERC-721 contracts operate under a monolithic token metadata architecture. Token URIs are either hardcoded into the smart contract or derived through deterministic logic, which limits the ability to introduce per-token variability. Moreover, reliance on off-chain resources such as IPFS introduces issues related to availability, mutability, and provenance.

Built by Xyxyx, the ERC-721F standard takes a fundamentally different approach. By delegating metadata construction to the mint function — and by allowing external systems to inject token-specific metadata at runtime — the standard promotes a modular and extensible architecture. For that, the ERC-721F integrates native Base64 encoding within the tokenURI schema as default.

svgString

The core functionality of ERC-721F is a parameter called svgString, which is encapsulated in the mint function. svgString permits the definition of tokenURIs at the time of token issuance, bypassing traditional metadata bottlenecks.

As a result, ERC-721F enables the creation of highly customized and self-contained tokens that, on the one hand, do not depend on off-chain infrastructure for data storage and, on the other hand, can be composable with any existing external system for data input.

ERC-721F and Xyxyx API

Unlike traditional ERC-721 contracts where the metadata URI is statically embedded, ERC-721F delegates metadata construction to external systems through the minting process. This design principle reflects a modular and extensible architecture, where third-party applications can dynamically determine token characteristics at runtime.

The ERC-721F standard is designed for seamless integration with the Xyxyx API, a REST API developed to automate and simplify the creation of contract deployments and injection of svgString values during the minting process.

By leveraging the Xyxyx API, the ERC-721F can be leveraged to programmatically generate and assign complex on-chain metadata to tokens, reducing the need for manual metadata construction and enabling integration with any existing system.

Conclusion

By decoupling metadata from rigid contract logic and empowering external systems to participate in metadata construction, ERC-721F provides advancements in modularity, extensibility, and metadata composability with any existing system.

Through ERC-721F, smart contracts no longer dictate the entirety of token metadata. Instead, they serve as programmable shells into which structured, dynamic data can be injected by any existing system — unlocking a wide range of potential interactions and designs.