Assets

Now that we've looked at how NFT smart contracts and metadata work, the last piece is the assets. Where are the actual image, video, and other multimedia files stored, and how are they connected to the metadata?

Asset Storage

Much like metadata, assets can be stored on-chain (in a smart contract), on decentralized storage (IPFS), or on centralized storage (a custom API, or other hosting providers like AWS).

The main thing to consider is whether your assets are static or dynamically generated based on user input or other factors.

Most NFTs use static assets: images, video files, or webpages. Whether an NFT collection has 3 video files or 3000 video files, IPFS is a great choice.

If you're looking for easy IPFS storage, consider https://nft.storage/. It's free for the foreseeable future (details on their site).

Some NFTs are created dynamically based on user input. For example, maybe the collector can pick the color of an NFT when they mint it. In this case, there are several options:

• If your assets are small files (SVG or tiny PNG), consider if you can generate them on-chain. Otherwise...
• Your assets can be an interactive webpage that you host on IPFS, and then you can customize the tokenURI function to add a query parameter
• You can upload a file to IPFS as part of your minting process (this is what https://ethblock.art/ does, for example)
• You can use a custom API that reads from your smart contract and returns an asset. This is a practical but not very "web3" solution.

If you're just getting started, uploading a folder to IPFS is probably the way to go. After that, especially if you're a developer, the other options can be fun to explore.

Metadata

For an NFT that's just an image, you can use the image field of the metadata JSON. If the NFT is any other kind of multimedia, e.g. audio, video, or webpage, this should go in the animation_url field, as described in the OpenSea Metadata Standards.