Crypto glossary
NFT metadata
NFT metadata is the data, usually a JSON file, describing an NFT's name, image and traits; where it is stored decides whether the NFT can break or change.
An NFT contract on Ethereum typically stores only the token ID and owner. A function called tokenURI returns a link to a metadata file, which contains the name, description, image link and attributes such as background or rarity traits. Wallets and marketplaces read that file to display the NFT. Other chains, such as Solana, have their own metadata programs but follow a similar idea.
Where the file lives matters enormously. If it sits on a company's web server, the image can disappear or be replaced whenever the server changes or shuts down, as happened with NFTs hosted by some failed platforms. IPFS links are content-addressed, so the data cannot be swapped without changing the link, but the files must stay pinned by someone. Arweave aims for permanent storage, and fully on-chain NFTs keep everything in the contract itself.
Before buying, it is worth checking whether the metadata is frozen or can be edited by the project, and where it is hosted. Mutable metadata enables legitimate features like reveals and dynamic NFTs, but also lets teams change art after sale. Marketplaces cache images, so a broken link may not be obvious at first.
Example
A buyer inspects an NFT's tokenURI and sees it points to a web server rather than IPFS; a year later, the project's domain lapses and the NFT shows a blank image on every marketplace.