What is ERC-721? How does it work?

The Ethereum blockchain introduced a revolutionary concept in the form of ERC-721, a standard for creating and managing non-fungible tokens (NFTs). Unlike ERC-20 tokens, which are fungible and can be exchanged one-to-one, each ERC-721 token is unique and cannot be replicated. This uniqueness has opened up a world of possibilities in the digital space.

The concept of ERC-721 started gaining traction with the launch of projects like CryptoKitties in 2017, which allowed users to buy, collect, and breed digital cats. The success of such projects highlighted the potential of NFTs to represent digital ownership in a variety of fields.

Also Read: What are Refundable NFTs (ERC-5507)?

CryptoKitties, a ERC-721 NFT
CryptoKitties, a ERC-721 NFT

How does it Work?

ERC-721 tokens function through smart contracts on the Ethereum blockchain. Each token is associated with a specific, unique asset, be it digital art, a collectible item, or any other form of unique digital property. These tokens are stored in digital wallets and can be bought, sold, or transferred, allowing for the proof of ownership and authenticity of digital assets.

Smart contracts are self-executing contracts with the terms of the agreement directly written into code. They enable the creation, transfer, and management of ERC-721 tokens, ensuring that each token is unique and its ownership is verifiable.


The applications of ERC-721 tokens are vast and varied. In the realm of digital art, they are used to prove the authenticity and ownership of digital artworks. These tokens can represent in-game assets in gaming, such as unique characters or items. They also have potential applications in digital identity, real estate, and other areas where uniqueness and proof of ownership are paramount. Here are some categories:

  • Digital Art: Artists can tokenize their artworks, ensuring authenticity and enabling easier transfer and sale in the digital realm.
  • Collectibles: Digital collectibles, like rare items or limited edition goods, can be represented as ERC-721 tokens, allowing for proof of ownership and liquidity.
  • Gaming: In video games, ERC-721 tokens can represent unique in-game assets such as characters, skins, or equipment, enhancing the gaming experience and adding value to player interactions.
  • Real Estate: Virtual real estate can be tokenized to represent ownership of digital land or properties in virtual worlds.
  • Identity Verification: ERC-721 tokens can be used for unique identity verification processes, potentially revolutionizing how personal identification is managed online.
  • Music and Entertainment: Musicians and entertainers can tokenize their work, such as exclusive songs or performance tickets, providing a new avenue for monetization and fan engagement.

For further reading, in our recent article ERC-721 vs. ERC-1155 NFTs, we go into detail about the different types of NFTs.

Pros and Cons

The ERC-721 standard has several advantages. It enables the creation of unique digital assets, which can foster creativity and innovation. The transparency and security of blockchain technology ensure that the ownership of these assets is easily verifiable and secure.


  • Uniqueness: Each token represents a unique asset, ensuring rarity and exclusivity.
  • Proof of Ownership: Provides verifiable and immutable proof of ownership for digital assets.
  • Transferability: Enables easy transfer and sale of digital assets without intermediaries.
  • Interoperability: ERC-721 tokens can be used across various platforms and applications that support the standard.
  • Innovation in Digital Rights Management: Offers new ways to manage and enforce digital rights and royalties.

However, there are also drawbacks. The Ethereum blockchain, like many other blockchain platforms, faces challenges related to scalability and environmental impact due to its energy-intensive nature. The market for NFTs is also subject to high volatility, which can pose risks to investors and creators.


  • Market Volatility: The NFT market can be highly volatile, leading to uncertain investment outcomes.
  • Scalability Issues: Ethereum network congestion can lead to high transaction fees and slower processing times. Layer-2 solutions are tackling this issue now.
  • Intellectual Property Concerns: Issues around copyright infringement and the unauthorized tokenization of artworks.
  • Limited Understanding and Adoption: The general public may have a limited understanding of NFTs and blockchain technology, hindering wider adoption.

Know how ERC-1155 Addresses these issues through batch mints, batch transfers and increased gas efficiency.

Some of the most well-known ERC-721 NFTs include CryptoKitties, one of the first and most popular NFT projects, and NBA Top Shot, which offers collectible highlights from NBA games. Digital artworks by artists such as Beeple have also sold for millions of dollars, showcasing the significant impact of NFTs in the art world. CryptoPunks was the first project to introduce the concept of an art collection on a contract and became the bedrock for the ERC-721 standard. As such, CryptoPunks are considered a staple collection to own.

Top NFT Projects

The world of Non-Fungible Tokens (NFTs) is rapidly expanding, with innovative projects leveraging the unique capabilities of ERC-721 tokens. These projects are not just redefining digital ownership but are also shaping new experiences in virtual worlds, gaming, and digital art. Among the plethora of projects, three have stood out for their innovative use of ERC-721 tokens: Bored Ape Yacht Club, Axie Infinity, and Blur.

Bored Ape Yacht Club: Redefining Digital Collectibles and Community

The Bored Ape Yacht Club (BAYC) stands as a groundbreaking project in the NFT space, making waves with its collection of unique ERC-721 tokens. Each token in this exclusive club represents a distinctively designed Bored Ape, serving not only as a digital collectible but also as a membership card to an elite virtual community. Owners of these NFTs gain access to a range of benefits, including exclusive events, social gatherings, and additional digital content. The BAYC has transformed the concept of digital collectibles by combining art with a sense of belonging and interaction among its members. The project has garnered significant attention and enthusiasm, attracting celebrities and collectors alike, and has become a symbol of status and community in the ever-evolving world of NFTs. Its success demonstrates the powerful combination of creativity, technology, and social engagement, setting a new standard for what digital art and community can achieve.

Axie Infinity: Reinventing Gaming with Blockchain

Axie Infinity has taken the gaming world by storm, introducing a blockchain-based game where players breed, raise, and battle creatures known as Axies. Each Axie is a unique ERC-721 token with its distinct attributes and strengths. Players can train their Axies, engage in battles, and even trade or sell them on the Axie marketplace. This model adds a new dimension to gaming, where players have true ownership of their in-game assets, opening up possibilities for earning through play and creating a vibrant economy around the game’s ecosystem.

CYAN: Pioneer in NFT Loans

Buying NFTs on CYAN is a simple 2 step process. We have made it super simple to buy NFTs on our website. You just need to connect wallet and approve the transaction.

Sorting and Filtering in Cyan's NFT Shop
Sorting and Filtering in Cyan’s NFT Shop
  • Connecting Wallet: No account creation needed; users can connect their wallets directly via the “Connect Wallet” option, supporting MetaMask, Wallet Connect, Unstoppable Domains, Rainbow, and Rabbit.
  • Buying Process:
    • Wallet connection not required for browsing the Shop page.
    • Over 107 Ethereum and 10 Polygon collections available for browsing in grid or list view.
    • Filters help select desired traits and pricing. Selecting an NFT opens financing terms for down payment and loan duration, with an option for automatic repayments.
    • Automatic Repayments deduct funds from either the user’s wallet or a Cyan Wallet, where NFTs on loan are held.
    • A Cyan Wallet is created upon the first purchase or loan, where purchased NFTs are stored until the loan is repaid.

CYAN also features easy NFT Loans (a.k.a. Buy Now, Pay Later) that help you pay for your purchases in multiple transactions and also allows users to sell the NFTs in just 1 click if they do not want the loan repayments anymore.

Each of these projects showcases the versatility and potential of ERC-721 tokens. From creating entire virtual worlds to transforming the gaming and digital art landscapes, ERC-721 tokens are at the forefront of the NFT revolution, providing innovative solutions for digital ownership and creation. As the NFT space continues to grow, these projects are likely to play a significant role in shaping the future of digital assets and online interaction.

NFT Staking

NFT staking is an emerging concept where users can lock up their NFTs in a smart contract to receive rewards. This mechanism is similar to staking in cryptocurrency, where holding and supporting the network is incentivized. NFT staking is gaining popularity as it provides NFT holders with a way to earn passive income while retaining ownership of their assets.

The largest project incorporating NFT staking is ApeCoin, with its native token, $APE. Owners of NFTs from the Bored Ape Yacht Club, Mutant Ape Yacht Club, and Bored Ape Kennel Club can stake their NFTs to earn a yield, paid out in $APE. This is one way to earn passive income in the NFT ecosystem, through the staking of ERC-721 tokens. Many other projects are following this mechanism design, including The Plague and Kanpai Pandas.


In conclusion, the realm of ERC-721 tokens represents a significant milestone in the digital world, offering new possibilities for ownership, creativity, and innovation. From the unique digital landscapes of Decentraland to the dynamic gaming experiences of Axie Infinity, and the empowering art platform Rarible, ERC-721 tokens are reshaping how we interact with and value digital assets. As we continue to witness the evolution of NFTs, it is clear that these tokens are not just a fleeting trend but a foundational element in the ever-expanding universe of blockchain technology. The future of digital ownership and creativity looks bright and boundless, with ERC-721 tokens leading the way.


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