Build your own marketplace in minutes

OpenSea provides a one-stop shop for creating your own customizable marketplace for your non-fungible token (NFT) project. Allow users to smoothly buy and sell your items, get custom stats and analytics, and earn revenue when your items get traded.


OpenSea Basic Integration

Integrate an existing mainnet ERC721 project into OpenSea

This page is designed for developers who have already written their ERC721 contract and wish to integrate it with OpenSea. However, if you're starting fresh, we recommend following the official OpenSea Developer Tutorial.

Viewing your existing items on OpenSea

Good news! If you've deployed your ERC721 contract on the Ethereum mainnet, your items are already tradeable on OpenSea. Just go to our listing flow to view your storefront.

Metadata API

If you haven't complied to the ERC721 metadata standards, your items may not show up on OpenSea as intended: they may be missing images, names, or descriptions. To fix this, you can provide OpenSea with a metadata API that provides this info. You can see all of the details on the exact format for this API here. An example API response would look like this:

  "description": "Friendly OpenSea Creature that enjoys long swims in the ocean.", 
  "external_url": "", 
  "image": "", 
  "name": "Dave Starbelly",
  "attributes": [ ... ], 

Typically, OpenSea use the tokenURI method in ERC721 to find the metadata API for items (you can learn about exactly how this works here). However, if you've already deployed your contract and didn't implement this method, you can send an API URL to [email protected] that conforms to the metadata standards and has the format:


While your API can have any URL, it is important that it takes in a token ID and returns data in the format described here.

Updated 2 years ago

OpenSea Basic Integration

Integrate an existing mainnet ERC721 project into OpenSea

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