When you buy an NFT, you're not just buying a picture—you're buying a unique digital certificate built on ERC-721, a technical standard on the Ethereum blockchain that defines how non-fungible tokens are created and tracked. Also known as non-fungible token standard, it’s what makes each NFT one-of-a-kind, unlike regular cryptocurrencies like Ethereum or USDT that can be swapped one-for-one. Without ERC-721, there would be no way to prove ownership of a specific digital item—whether it’s a pixelated ape, a virtual land plot, or a song with a single copy.
ERC-721 relates directly to NFTs, digital assets that can’t be exchanged equally because each has unique data attached. This is different from ERC-20, the standard used for most cryptocurrencies that are interchangeable. While ERC-20 tokens like LINK or UNI are like cash—any one unit is the same as another—ERC-721 tokens are like collectible trading cards. Each has its own ID, history, and owner. That’s why you can’t swap one Bored Ape for another and expect the same value. The blockchain remembers who owns which one, and no one can fake it.
ERC-721 enables blockchain tokens, digital representations of assets that exist on decentralized ledgers. It’s used in digital art marketplaces, game items, virtual real estate, and even ticketing systems. Projects like CryptoPunks and OpenSea rely on ERC-721 to prove authenticity. But it’s not magic—it’s code. Every NFT created with ERC-721 has a unique token ID, a contract address, and metadata that links to its image or file. That metadata is often stored off-chain, which is why some NFTs disappear if the server hosting the image goes down.
People often confuse NFTs with the file they represent. Buying an NFT doesn’t mean you own the copyright to the art. It means you own the token that proves you’re the verified owner of that specific version. That’s why the ERC-721 standard matters—it separates ownership from usage rights. If you buy an NFT of a song, you don’t get the right to play it in a club unless the creator says so. The token proves you have it. Everything else depends on the terms written into the smart contract.
Most NFTs you see today run on Ethereum because ERC-721 was the first widely adopted standard for unique tokens. But it’s not the only one. Newer standards like ERC-1155 allow for both fungible and non-fungible tokens in one contract, making them more efficient for games and collectibles. Still, ERC-721 remains the most recognized and trusted. It’s the foundation of the NFT boom, and even today, nearly every major NFT project you hear about uses it.
What you’ll find below are real stories about what happens when NFTs go wrong—projects that vanished, airdrops that never delivered, and tokens that looked like NFTs but weren’t built on solid ground. Some posts expose scams hiding behind the ERC-721 label. Others show how people actually use these tokens in practice. There’s no hype here. Just what’s real, what’s broken, and what you need to know before you click "Buy."
NFT metadata is the hidden data that gives digital assets their identity, traits, and value. Learn the core structure, storage options, common mistakes, and how to make sure your NFTs last.
