ERC721x — A Smarter Token for the Future of Crypto Collectibles

ERC721x is an extension of ERC721 that adds support for multi-fungible tokens and batch transfers, while maintaining full backward compatibility.

Luke Zhang
Sep 10, 2018 · 4 min read


First, a Little Background

Here at Loom Network, we’ve been hard at work on Zombie Battleground, a 100% on-chain collectible card game that’s targeted at mainstream audiences.

Things like:

  1. Transfers should cost very little gas, even if the player is transferring a large quantity of items. For example, someone might want to transfer a few hundred very cheap cards that are worth little individually, but quite valuable in bulk.
  2. One contract should contain multiple “classes” of items. In a card game like Zombie Battleground, not every item is unique. There may be thousands of identical copies of the same card owned by different users, and the contract should be able to recognize that these items are part of the same class.
  3. Compatibility with marketplaces, wallets, and existing infrastructure (e.g. Etherscan). Wallet and marketplace makers provide a valuable service to the community, and it makes sense to leverage their existing work.

The Current Landscape

Our Approach: Extending ERC721 with ERC1178

Out of all the existing solutions to this problem, the one that best suited our needs was ERC1178.

  1. It has very little bloat — just the bare minimum to implement the necessary features. The fewer things added, the better the chances are that it’s secure, because it deviates less from battle-tested code.
  2. It’s really useful for things beyond just games — for example, creating a token that can represent preferred, common, or restricted shares of a company.

We call it ERC721x:

ERC721x adds the support necessary for real world usage of crypto-collectibles, with a compatibility wrapper to make it fully backward compatible with existing ERC721 services. It is open source on the Loom Network GitHub.

Real World Usage

ERC721x is immediately usable with any ERC721-compatible wallet, marketplace, or service.


Beyond the technical bits that make up blockchains, the spirit of blockchain tech is equally (if not more) important.

It’s these two principles that led us to create the new ERC721x, specifically for crypto-collectibles, and open source it for the crypto community.

Get started now on the official

Loom Network

🛸 The production-ready, multichain interop platform for serious dapp developers —

Thanks to James Martin Duffy, 🤖 Robert, and Mohit Tater

Luke Zhang

Written by

Co-Founder at Loom Network

Loom Network

🛸 The production-ready, multichain interop platform for serious dapp developers —

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade