In this Etherscan Tutorial, we'll take a look at how the Etherscan API makes it easy for us to query the transaction history for an address. This will help us build a more reliable system.

OpenSea is annoying. Their site goes down all the time, everyone complains about their fees, and you have to fill out an application and wait for days for a response if you want an API key.

I have several different apps where I need to know what NFTs a user owns. Up until recently I was using the OpenSea API because it was the easiest, fastest thing to do.

Now, they've made it more complex, so I'm looking for a more reliable method.

Instead, we'll make use of Etherscan and their free, open API to query a user's transactions in Javascript, and then we'll parse those transactions to see which NFTs they still own.