ERC721 Contract: Adding Contract Level Metadata?

Question

I am trying to implement contract level metadata so "description", "image", external_link": etc show up on marketplaces, particularly OpenSea.

I have done an extensive search of the forums and nothing has addressed this already, so hoping this thread will shed some light.

I have added the following lines in Remix:

string _contractURI = "https://MY-CONTRACTURI-METADATA.com

function contractURI() public view returns (string memory) {

return _contractURI;

}

This actually successfully allows contract level metadata to shows up on OpenSea!

However, OpenSea doesn’t refresh from the JSON URI after the first time – it seems to be set once and cannot be changed.

Is this correct?

OpenSea documentation and forums do not offer any advice.

Next, the code compiles and deploys correctly to testnets, but it doesn’t load the ABI interface for read and write contract like the example code given in Contracts Wizard etc.

If I remove that string and function and recompile and redeploy the contract to testnets, the ABI interface for read and write contract LOADS.

What am I doing incorrectly here?

Answer 1

I struggled so much to find how to make this work but at the end was so simple.

create a .json file with the metadata and serve it with a simple http server

ie. if your file name is metadata.json your code should look something like this

string _contractURI = "https://yourDomain.com/metadata.json"

function contractURI() public view returns (string memory) {

return _contractURI;

}

OpenSea Documentation explicitly says URL https://docs.opensea.io/docs/contract-level-metadata

Edit: I tested this solution in an ERC1155 :D I suppose is the same for ERC721