How to create and sell an NFT in OpenSea?

como crear un NFT
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NFTs have been a cultural phenomenon in 2021, and are constantly in the news. And with some creators making millions from NFTs, it’s understandable that you might want to try your hand or play with this technology and get to know it better.

In this article we are going to explain how to create an NFT using OpenSea, which is one of the most popular marketplaces. But before we get to that point, let’s cover some of the basics of what an NFT is. If the process seems too complex, take advantage of the services of a cryptocurrency and blockchain advisor.

In this guide we will explain how to create your first NFT.

First of all you must create or have access to a wallet. We recommend you to use Metamask.

If you don’t know how to open a wallet I recommend you to read this post first: How to create a wallet in MetaMask

Once you have your wallet ready, you must log in to OpenSea.

From, go to your profile icon and click on “Create” in the top right corner.


Upload your NFT to OpenSea

After clicking the Create button, you will be taken to the new item creation page. To get started, click on the box with the image icon, which will allow you to upload the file you are going to sell as an NFT (be sure to note the file size and file type limitations above the selector).


What file formats can I use to create my NFT?

You can use a variety of file formats for images, videos, audio or even 3D models to make your NFT.

The maximum file size supported is 100 MB, but we recommend keeping it under 100 MB for faster loading.


Once you have added the file, give it a name or title. You can also use the “External Link” field to add URL that points, for example, to your website or Twitter account. You can also use the “Description” field to give your potential buyers a little more context as to what your NFT is.

Below those fields, you can choose a collection for your NFT if you’ve set one up, as well as add properties, levels or statistics that can basically act as metadata.

If you are selling an NFT that could act as a video game character, for example, this is where you would put its information.

If you’re selling a piece of artwork, you can use the properties panel to add information about it, such as medium, year, etc.

However, all of these fields are optional, so many people will probably ignore them.

OpenSea also allows you to add text that acts as unlockable content, which the buyer/owner of the NFT will be able to see.

You could use this activatable field to include something like an invitation link to a private Discord channel, a code to redeem something on an external website, or even just a thank you message for the purchase.


Select the Blockchain for your NFT

After those buttons and fields is the drop-down menu to select which blockchain you are going to use for your NFT: the Ethereum blockchain or the Polygon blockchain.

For this example we’re going to go with Polygon, as it currently doesn’t require any fees. If you are minting with Polygon, you will also have the option to mint multiple copies of your NFT.

Once you’ve chosen your blockchain, you’ll want to double-check everything.

OpenSea allows you to change the metadata afterwards, as long as you haven’t put it up for sale. It’s good practice to make sure everything is in order before you do anything blockchain-related.

Note that afterwards you won’t be able to change which blockchain the NFT is on.

Once you are ready, you can click the Create button.

How to sell your NFT on OpenSea

Depending on the options you’ve selected and the type of file you’re selling as an NFT, there may be a bit of a wait while it loads. When it finishes, you will see a screen that says your NFT has been created.

With your NFTs listed on Ethereum or Polygon, you’ll have the option to create an ad for a fixed price. On Ethereum, you’ll have the option to create a timed auction as well.

In the case of a fixed-price ad, you just put in the amount you want to sell the item for (which is listed on Ethereum, but will give you an approximate dollar amount below) and choose how long you want the ad to be available for.

In Ethereum, if it’s your first NFT, you’ll need to do a one-time approval transaction to “initialize” your Wallet, which we’ve already talked about. To do this, you will need to have Ethereum in your wallet.

The money from this transaction only goes towards the gas fee, not an OpenSea fee, so its cost depends entirely on how much Ethereum Gas fees are at the moment. At the time of writing this post prices are around $240 to $450, so you may want to wait until the price comes down – you can use Ethereum Gas Station to monitor transaction costs.

Once you have approved and signed all transactions, your NFT will be put up for sale on OpenSea.

What should I do now?
If you have more questions and want to know how we work, contact us and one of our consultants will contact you for advice. For further information on this and many other topics you can check out other articles in our blog where you will find references on this, and many more topics. If you liked this article, you can share it on LinkedIn, Facebook or Twitter by clicking on the icons below. I’m sure you have acquaintances who will like it as much as you do.

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