Getting Started

This tutorial will show you how to go from start to finish listing your item on OpenSea. We'll walk you through how to structure your metadata, how to view an item on OpenSea, and how to test out the auction flow. As an example, let's suppose we're building a game called "CryptoPenguins", in which penguins can battle each other on the blockchain.

1. Write your ERC721 token contract

ERC721 is the latest standard in non-fungible tokens. To be listed on OpenSea, your items should adhere to the latest Open Zeppelin implementation of ERC721.

2. Structure your token metadata

Whether you're building a game, collectible, or something completely new, you'll typically want to show some information about each game item. It is often wise to host some of this metadata off-chain, as on-chain storage can be rather expensive. You have a couple options:

Option 1: Host your metadata on your servers

If you host your metadata on your servers, OpenSea can pull in data and immediately list your items on our site. Simply implement the tokenMetadata function in your contract like so:

contract CryptoPenguin is ERC721Token {

    function tokenURI(uint256 _tokenId) public view returns (string) {
        // return "https://api.cryptogame.io/penguins/{_tokenId}"      
    }

}

Your tokenUri function in your ERC721 asset should return an HTTP URL, such as https://api.cryptogame.io/penguins/3. This URL can return a JSON blob of data with the metadata for your token. The data should be structured as follows:

{
    "imageUrl": "https://api.cryptopenguins.io/penguin-photo-abcdef.png",
    "externalUrl": "https://cryptopenguins.com/penguin/3",
    "description": "I like skiing, snowboarding, and eating fish.",
    "name": "Herbie the Penguin",
    "properties": {
        "color": "black",
        "stamina": 45,
        "health": 32.1
    }
}

Option 2: Host your metadata with OpenSea

This option is coming soon! We'll provide you with a REST API for updating metadata about your token. If you're interested in this option, please e-mail [e-mail]

3. View your items on the OpenSea Rinkeby site

Now that you've provided a standard API for your item metadata, you'll immediately be able to view your items on OpenSea if you deploy your contract on Rinkeby. To view an item, simply navigate to this URL:

https://rinkeby.opensea.io/assets/<your_contract_address>/<token_id>

where your_contract_address is the address of your contract and token_id is the id of your item.

If all goes well, you should see your item show up with it's image, name, description, and any properties you included. If your account owns that item, you should be able to put it on auction using the "Sell" button.