ERC-1155 Token Standard: Fungible and Non-Fungible Assets Explained

Semi-fungible tokens are a hybrid category of digital assets that combine characteristics of both fungible and non-fungible tokens. Using the example of a concert ticket to see The Beatles' last performance, a semi-fungible token initially has face value and can be exchanged for an identical ticket (same band, date, seating area). However, once the event concludes, the token transforms into collectible memorabilia with entirely new value and can no longer be exchanged for valid tickets. This hybrid nature allows tokens to serve different purposes at different stages, representing both utility and collectibility.

The video explains the key distinction between fungible and non-fungible tokens. Fungible items (like money) can be exchanged for other items of equal value - a $10 bill is interchangeable with another $10 bill. Non-fungible tokens (NFTs) are unique digital items that cannot be replaced by an identical substitute. This uniqueness is what gives NFTs their value, as each token represents a one-of-a-kind digital asset that cannot be duplicated.

NFT stands for Non-Fungible Token, which translates to 'tokens não fungíveis' in Portuguese. A fungible item is something that is interchangeable or substitutable by something of equivalent value, like currency or a shoe. In contrast, an NFT is non-fungible, meaning it is unique and cannot be replaced by another item. Each NFT possesses unique characteristics, such as a digital certificate of authenticity. NFTs are used to represent digital items including collectibles, digital artworks, event tickets, and other digital assets that have value in the digital economy.

A Non-Fungible Token (NFT) is a digital token that represents a unique item or piece of content. The term 'non-fungible' means the item cannot be replaced with an identical substitute - for example, a handwritten note is non-fungible because no other note can replace it, just as the Mona Lisa cannot be replaced by another painting. This uniqueness is what gives NFTs their theoretical value.

NFT stands for Non-Fungible Token. Fungible means replaceable by another identical item or mutually interchangeable (like one dollar being the same as another dollar). Non-fungible means the opposite - each item is unique and cannot be replaced by an identical substitute. In the digital world with its limitless facsimiles, non-fungible is particularly significant because digital content can normally be infinitely copied.

The ERC-1155 token standard, created by Engine Coin's co-founder, is a new standard for defining tokens on the Ethereum blockchain specifically designed for video game items. Unlike previous token standards where each token required its own contract, ERC-1155 allows multiple tokens to be stored in a single contract with minimal data required to distinguish between them. This standard enables easier atomic swaps between tokens and supports both fungible tokens (interchangeable items like ammunition and health kits) and non-fungible tokens (unique items like armor and weapons). This represents a significant advancement for creating digital scarcity and ownership of in-game items on the blockchain, allowing players to truly own their in-game items rather than just having access to them within a game.

ERC-1155 is a multi-token standard that enables efficient batch trading of multiple items in a single transaction, solving the scalability limitations of ERC-721 which required individual smart contracts for each item. This standard allows game developers to create economies with fungible tokens (like currency) and non-fungible tokens (like unique items) within a unified system, enabling secure virtual item ownership and trading without centralized control.

ERC-1155, created by Enjin in 2017, enables unique and fungible items in one smart contract, unlike ERC-20. This allows games to have gold (fungible), health kits (fungible), unique swords (non-fungible), pets, and character NFTs simultaneously. It works like a vending machine for tokens, reducing transaction fees for game developers. The standard is now supported by most marketplaces and is most efficient for minting large collections (10,000+ items). Utility extends beyond art to include in-game items, virtual world assets, and business applications, with potential for crafting, player-created content, and permadeath mechanics.

ERC-1155 is a gaming token standard enabling native support for multiple token types in a single smart contract. Unlike ERC-20 (fungible tokens) or ERC-721 (unique NFTs), ERC-1155 allows one smart contract to handle both fungible tokens and non-fungible tokens, simplifying integration for game developers. Metadata for items can be stored off-chain in game software rather than on the blockchain, reducing storage costs while maintaining provable supply benefits. Engine is developing native integrations with ERC-1155 support, allowing seamless minting, sending, and receiving of tokens directly from games without transaction costs or latency.

The Monks contract uses ERC-1155, a multi-token standard designed for gaming applications, allowing multiple tokens within a single contract. Each character has 14 genome types (Spiritual, Enlightened, Mercenaries, Warriors, Elite Warriors, Zombies, Zombie Priest, Zombie Warlock, Eternals, Nuns, Degens) that define layer structures. Every Monk has 10 layers for item placement, with different character types having varying numbers of available slots. Elite Warriors have additional layers, while Eternals have a static genome with no editable layers. Each Monk has three era-specific sub-genomes: Ancient Times, Modern, and Futuristic, with era-specific item restrictions. Items are layered on top of each other in a specific order, starting from the skin layer. Each item is an NFT that can be bought, sold, and traded, with each Monk currently limited to one item per layer. Users can upload images through the Monks API and specify which layer they want items on. Official items require team approval, while users can create their own separate items. Items have a separate OpenSea collection with IDs starting from 3333 (IDs under 3333 are Monks). When items are minted onto a Monk, they are burned and minted directly onto the Monk's contract, retaining identifiers but disappearing from the market until removed.

Auditors must understand gas optimization since each transaction costs users money. They should study leading protocols like Uniswap to learn advanced features like multi-call implementations. Auditors must understand token transfer methods (call, send, transfer) and upgradability patterns, which create vulnerabilities if admin access is compromised. Assembly language knowledge helps optimize code. Auditors should continuously update knowledge about new vulnerabilities, optimization techniques, and industry standards. The field requires ongoing learning and adaptation to emerging patterns.

On-chain databases like Moddable are designed for gas efficiency, particularly for applications like games that require storing large amounts of data. When auditing smart contracts for gas optimization, focus on three key areas: (1) Structs - check for inefficient storage usage, (2) For loops - look for repeated storage reads and inefficient patterns, (3) Storage variables - identify opportunities for caching and reducing SLOAD operations. Key resources for gas optimization include Vectorized's Twitter (sharing optimization techniques), Gaslight project (efficient airdropping), and Huff assembly language. Huff allows for more granular gas optimization than Solidity but is still in early development stages and not suitable for production contracts requiring security guarantees. Understanding the EVM at a deeper level provides significant benefits: it enables more effective gas optimization, helps identify vulnerabilities not visible at the Solidity level, and provides a competitive advantage in the smart contract development field.

Advanced gas optimization requires balancing efficiency with security. Transaction data costs 16 gas units per byte, making data inclusion expensive. Payable functions cost less than non-payable functions because they don't require checking for Ether inclusion. State variables are permanently stored on the blockchain and consume significant gas, while local variables exist only during function execution. Using state variables unnecessarily can cost thousands of gas units more than local variables. Variable packing stores multiple small variables in a single 32-byte slot to reduce gas costs, with unused space padded with zeros. Advanced optimization techniques include reducing state changes by performing calculations in local variables first, using unchecked arithmetic when overflow is impossible, and leveraging memory instead of storage. Developers must balance optimization with security, as unchecked operations can introduce vulnerabilities. Industry best practices demonstrate that optimization should only be applied when security risks are well-understood.

Writing gas-efficient contracts follows four core principles: designing architectures that minimize on-chain data storage, prioritizing cheap operations over expensive ones, applying known optimization patterns like array length caching, and always benchmarking different implementations. Professional auditing requires thorough protocol understanding through documentation review and community engagement, followed by systematic identification of expensive operations. The key insight is that fundamental code restructuring often yields greater savings than incremental optimizations. Comprehensive reporting with clear explanations and quantified gas reductions is essential for competitive audits. Best practice suggests performing gas optimization before security audits to isolate efficiency improvements from correctness verification. Automated bots increasingly find common optimizations, making creative architectural decisions the primary frontier for meaningful gas savings.

Loops over user-controlled arrays pose critical risks—excessive growth can exceed block limits and freeze contracts. Re-entrancy protection should only be added to functions transferring ether or making external calls. Reading storage inside loops is expensive (800 gas per read); calculate array lengths once and store in local variables. Unchecked blocks eliminate overflow/underflow checks when results are guaranteed valid. These optimizations compound significantly, especially for large arrays, making careful function design essential for gas efficiency.