What is an NFT?

Zeevo - Published on November 14, 2021

There is a lot of confusion on what an NFT is and this article aims to educate. The goal is to truly learn what NFTs are faithfully and without the influence of bias or confusing analogies.

Nonfungible Token, or NFT, is a unique unit of data that is not interchangable with any other unit of data. It is in constrast to fungible items such as a dollar bill or Bitcoin where each unit is equivalent to one another and can be easily swapped with one another without losing value. Typically, we see NFTs implemented on a Blockchain such as Ethereum. The benefit of storing them on a decentralized Blockchain is that they will be distributed to many computers and also be available for anyone to see at all times. Ethereum's Smart Contract platform is one of the most popular methods of implementing NFTs because it is a strong chain with strong developer tooling. Assuming the Smart Contract is correctly implemented, once an NFT is established on the Blockchain, a sense of scarcity, genuineness, and permanence emerges leading to NFT markets where people buy, sell, and trade NFTs as assets.

The methods of interacting with NFTs on a Blockchain are simple. Owning an NFT is simply assigning your public Address as the owner of a unit of data within a Smart Contract. Transfering an NFT is re-assigning the owner to a new Address. Selling would consist of a payment to an address, followed by a Transfer.

What an NFT is not

There is a common misconception that NFTs are literal images distributed on the Ethereum Blockchain. This is absolutely not the case. The vast majority of NFTs minted are high quality PNG or JPEG file formatted pictures that exist off of the Blockchain (this is commonly referenced as being off-chain). The community has chosen the IPFS system to help in the integrity of NFTs. For all intents and purposes, this is a good decision. The IPFS (Interplanetary File System), is a distributed database of files similar to that of Bit Torrent. Files are uploaded permanently and are assigned an IPFS Hash: A unique ID for each file. IPFS operators help provide integrity to files by backing up portions of the entire IPFS. Together, a strong and permanent network of file systems creates a database of files that cannot be easily deleted or changed.

However, there does exist projects that encode image data directly onto the Blockchain usually in the format of low-size pixel map or pixel art styles. The only way to determine if your NFT is a quality one is to look at your NFT's Smart Contract for how it is implemented.

What an NFT is

Not all NFTs are created equally. Some are higher quality than others, and many NFT Contracts were created with permanent vulnerabilities and fundemental misunderstandings on how the internet works. There are popular projects that continue to trade high volumes that are low quality and this can only be attributed to a lack of knowledge by participants of the underlying code.

An NFT is a Smart Contract that stores data on a Blockchain. The Metadata must contain NFT IDs, Ownership information, and NFT Metadata.

Essentially, NFTs are unique IDs that have owners, as well as small bits of additional Metadata assigned to each ID that describes it. Metadata is particularly important to understand as this is what differentiates Good NFTs from Bad NFTs


What is NFT Metadata?

These can take many forms and some offer much more security, longevity, and accuracy than others.

IPFS HashesA string of characters indicating where users can go off-chain to find the original NFT image or additional information
IPFS Gateway URLsSimilar to an IPFS Hash, this is an internet facing link to a public IPFS Gateway. IPFS Gateways are websites that allow users to view IPFS data. There are no guarantees that this domain will be around forever, or will remain in honourable hands.
Proprietary API URLsWebsites that the NFT project owners host to provide additional information about their NFTs or for the original images.
Image encodedless common, but potentially the most "accurate" implementation as image data is encoded directly into the Smart Contract itself so that all data is on-chain. These typically take the form of pixelated images as there are limits to the amount of data a Smart Contract can reasonably write to the blockchain

In terms of which NFT Metadata is "better" can be a matter of the goal of the NFT project. If the NFT project is interested in minting high quality images, then an IPFS Hash is probably the best way to go. If a project is interested in the the purity and security of the product that is being sold, encoding the image directly onto the blockchain is the best way (However this has limitations to how big the images can be). Any NFT minted that has its Metadata tied to the developer's website or that of any other personal domain name, including IPFS gateways, can be considered unbacked by decentralized infrastructure (whether IPFS or Blockchains), and thus should not be valued at all. There is no guarantee that the website containing your NFT information with always be live serving your NFT Metadata. And of course, a good name and description along with the afformationed data is desirable.

What makes an NFT valuable?

It can be hard to understand what makes NFTs seemingly sell for such high prices. I will offer a few theories on what can make an NFT valuable to me.

A Reputable Smart Contract

A Smart Contract that is in someways unique, clever, the first, a community favorite, or other reasons can bring value to the NFT's it mints.

A Smart Contract that publishes their ABI and Source Code

This is a necessity. Smart Contracts that do not publish their Application Binary Interface prevent outside individuals from interacting with them. Essentially, those with non-public ABIs should have their legitimacy scrutinized and should not be interacted with.


Older Smart Contracts with a larger transaction history can help being legitimacy to their NFTs.

Image Encoded NFTs

Smart Contracts that encoded their NFTs directly to the Blockchain are often seen as more philosophically pure than those that have off-chain data.

Egregious offender: Lazy Lions NFT

To illustrate the points made here, we can look at a particularly bad NFT: Lazy Lions.

At the time of writing this, Lazy Lions has 17.3k of Ethereum traded by volume. That is almost $8,000,000! Lazy Lions is a collection of NFTs representing profile pictures of Lions. They claim that each NFT is unique and that each was created programmatically from a selection of different traits and colors. The idea here is that "rare" NFTs will be organically created due to the random selection of traits. For example, if during the creation of the collection, only one NFT obtained the "Blue" trait, then that member would be exceedingly rare (and thus, worth more money). However, their algorithm for programatically generating NFTs is closed-source so it is impossible to know just how organic the Lions really are. We can view this NFT Smart Contract's Metadata on Etherscan.

We can view this entire collection on OpenSea.

Lazy Lions Collection

OpenSea lets anyone viewing NFTs the ability to see the NFT Contract Address and NFT ID. We can use these together to view the NFT Metadata. For example, Lazy Lion #7182 (I selected this at random) has a Contract address of 0x8943c7bac1914c9a7aba750bf2b6b09fd21037e0 and ID of 7182

We can use Etherscan's Read Contract feature to conveniently query the Contract for NFT Metadata. Executing the tokenURI method with an argument of 7182 will get us the Token's URI, an off-chain location that has additional information.

Lazy Lions Collection

The method returned a string and we now have an off-chain place to visit: https://www.lazylionsnft.com/api/7182

This is a NFT with it's Metadata in the form of a Proprietary API. Visiting this link returns us JSON:

"name": "#7182",
"tokenId": 7182,
"image": "https://gateway.pinata.cloud/ipfs/QmT7n9pymJ8z6rQH9hAD48LBMuxb5PhQAZCmFXLjHpk6bV",
"external_url": "https://www.lazylionsnft.com/",
"attributes": [
{ "trait_type": "Background", "value": "Iron" },
{ "trait_type": "Body", "value": "Standard" },
{ "trait_type": "Bodygear", "value": "Police Uniform" },
{ "trait_type": "Earring", "value": "Nothing" },
{ "trait_type": "Eyes", "value": "Stoner" },
{ "trait_type": "Headgear", "value": "Halo" },
{ "trait_type": "Mane", "value": "Top Knot - Fire" },
{ "trait_type": "Mouth", "value": "Big Smile" }

We can see the image is the form of an IPFS Gateway. This, however, does not mean much for the quality of this NFT as this IPFS information is already behind a proprietary API.

Attaching NFT Metadata as an off-chain link such as lazylionsnft.com/api/7182 gives the owners of lazylionsnft.com the ability to change NFT Metadata whenever they desire! NFTs like this have essentially none of the benfits of being on the Ethereum Blockchain and are nothing more than links to someone else's website. There is no sense of permanence, no data integrity, and no guarantee that Lazy Lions NFT won't just be a collection of defunct links years from now.

Image Encoded NFT: CryptoPunks


A lot of the success of CryptoPunks can be attributed to the fact that it is an Image Encoded NFT. This means that every NFT is solely on the Blockchain: No IPFS, no off-chain API, no chance of compromise or change of Metadata.

Let's look at the data that is on-chain regarding a CryptoPunk NFT.

Some of the methods this Contract offers are:

  • punkAttributes
  • punkImage
  • punkImageSvg

--> punkAttributes(6027)

Male 3
Shaved Head
Classic Shades

--> punkImage


--> punkImageSvg

<svg xmlns="http://www.w3.org/2000/svg" version="1.2" viewBox="0 0 24 24">
<rect x="8" y="5" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="9" y="5" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="10" y="5" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="11" y="5" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="12" y="5" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="13" y="5" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="14" y="5" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="7" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />
<rect x="8" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#5e4c37ff" />
<rect x="9" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#5e4c37ff" />
<rect x="10" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#5e4c37ff" />
<rect x="11" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#5e4c37ff" />
<rect x="12" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#5e4c37ff" />
<rect x="13" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#5e4c37ff" />
<rect x="14" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#5e4c37ff" />
<rect x="15" y="6" width="1" height="1" shape-rendering="crispEdges" fill="#000000ff" />

As we can this is a map of X, Y coordinates in an SVG format. We can open this as an SVG file with any SVG viewer:


Just having the NFT ID, we can see NFT attributes and render the image. All of this information has come from the Ethereum Blockchain and no off-chain data sources.

NFTs like these are some of the most expensive to mint. However, they are the most pure in terms of Blockchain philosophies, offer the best security, and have guaranteed data permanence.

Checking NFT Metadata for yourself

If you have the Smart Contract Address, ABI, and an Ethereum node, you can check NFT data yourself. This is the most reliable way to know what you are getting for your purchase.

const Web3 = require('web3');
const net = require('net');
// Contract ABI
const abi = require('./abi.json');
// Use an Infura Ethereum node. Better yet, use your own localhost.
const web3 = new Web3(
new Web3.providers.HttpProvider('https://mainnet.infura.io/v3/<INFURA_API_KEY>'),
// Contract address
const contract = new web3.eth.Contract(abi, '0x8943c7bac1914c9a7aba750bf2b6b09fd21037e0');
// Query the tokenURI method of the Contract
.then((res) => {


NFT exchanges like OpenSea and Foundation present their NFTs like they are all the same -- And they are not.

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