Of all the blockchain-based games that have captured the attention of the public over the years, none has done more to advance the adoption of non-fungible tokens than CryptoKitties. At the height of its fame, the game’s popularity was so widespread that it commanded over 25% of all network traffic on the Ethereum platform.

Amazingly, at its peak, Founder Cat #18 was sold for 253.3368 ETH ($164,000). While the average price for virtual cats has since declined, the game still commands a large following in the crypto community and generates significant media attention. In this guide, we’ll go through the history of CryptoKitties, review its gameplay features, discuss what you need to get started and show how to buy virtual cats.


Created by the Canadien startup Axiom Zen in 2017, CryptoKitties had the rare distinction among blockchain games of becoming immediately popular upon its release. The game’s concept was so unique that just a day after its smart contract deployment on November 22, 2017, CryptoKitties was one of the top three most active contracts on the Ethereum blockchain.

The game officially launched on November 28, 2017, and by December 2, 2017, a cat under the name of Genesis sold for a whopping 246 ETH, equal to $117,712 at the time. By December 5, 2017, the game had processed over $5 million in transactions, and it was clear that CryptoKitties had become a cultural phenomenon.

Although the median price for virtual cats fell at the start of 2018, the game’s widespread appeal was too lucrative for investors to pass up. On March 20, 2018, Axiom Zen announced that CryptoKitties would be spun off into its own company called Dapper Labs, which soon raised $12 million from several top venture capital firms and angel investors.

Network Congestion

Despite the immediate success of CryptoKitties, the rapid rise in the game’s player base led to a surge in traffic both on the CryptoKitties site and the Ethereum network as a whole. The overall network congestion, which manifested itself through processing delays and lag time, exposed the vulnerability of the Ethereum network and blockchain technology in general to overcrowding.

As a response to the crisis, the gas fee for site transactions skyrocketed, and CryptoKitties was forced to raise its breeding fees from 0.002 to 0.015 ETH to compensate for the rising Ethereum gas prices. Additionally, the surging NFT volume indirectly led to the launch of OpenSea, an NFT marketplace that has since become the most widely-used NFT exchange in the world.


Compared to the hundreds of other blockchain-based games, CryptoKitties has a relatively simple premise. Players can purchase, breed, and trade virtual cats that have different traits, which makes certain cats more valuable than others due to differing levels of rarity.

Every virtual cat carries 48 distinct genes that manifest themselves as “cattributes,” with traits passed down from a male and female cat to their offspring. There are 12 cattributes in total: pattern, mouth shape, fur, eye shape, base color, accent color, highlight color, eye color, optional wild, environment, purrstige, and secret.


As CryptoKitties operates on Ethereum’s underlying blockchain network, ETH is the native currency that powers the game, and those who want to participate in buying and selling must acquire an Ethereum wallet in order to hold their tokens.

Additionally, each CryptoKitty is an NFT – defined as a digital proof of ownership for an item. Each cat is a completely unique NFT and owned entirely by the user, whose transaction is validated through the blockchain. CryptoKitties cannot be replicated and cannot be transferred without the user’s permission even by the game developers.


One of the most frequent criticisms of CryptoKitties is that it lacks a traditional objective, with certain players stating the game has “no goal.” In some sense, the entirety of gameplay consists of buying, breeding, and selling cats. Unlike past digital games such as Tamagotchi or Pokemon, where players could nurse or raise their pets, CryptoKitties offers limited interaction time and instead focuses on specific traits that can be passed onto offspring.

While many of these objections are valid, what critics fail to take into account is that CryptoKitties offers a unique entrance into a Web 3.0 ecosystem. In Web 3.0, players are able to monetize their investments and efforts outside the platform. These assets can also be transferred to other digital experiences, creating an entirely new Internet economy that can be converted to real-world currency.

Simply put, CryptoKitties allows players to earn money in ways never thought possible before. Like any other asset, the value of a cat can appreciate or depreciate based on the market, meaning it’s possible for owners to sell their NFTs for far more than they bought them for, or in certain cases, lose money on their sale..

Money aside, there’s also the fun of creating unique digital animals whose traits are often outside of the breeder’s control. No one ever knows for sure how their offspring is going to turn out – making it possible for happy accidents to occur and leaving the door open for that special kitty that could be worth extremely rare.

Types of Cats

In order to navigate the CryptoKitty marketplace, it’s important to understand the various types of cats that players can own. There are four main types of cats: normal, exclusive, purrstige, and fancy. As a normal cat’s appearance is based solely on its genetic cattributes, we will dive deeper into this cat type in the Genes section of this article.

Exclusive Cats

The rarest type of cat available, exclusive cats are released by CryptoKitties to commemorate special events and community members. Often, an exclusive will be the only cat of its kind, like Cathena, the 500,000th cat created on the CryptoKitties site. Because of their rarity, exclusives are worth far more than the average cat, with Cathena’s current listing price standing at a stunning 500 ETH. However, exclusive cats cannot be bred – which means that breeding an exclusive with another cat will just result in a normal CryptoKitty.

Fancy Cats

Less rare than exclusive cats, fancy cats are nevertheless a highly coveted item in the CryptoKitty universe. Fancy Cats are a series of special cats identified by their unique artwork and badge.

When CryptoKitties first released Fancies, players were able to breed as many of them as they wanted. However, the developers have since imposed controls on the number of fancy cats that can be produced, making them all limited edition. Now, once you hit a Fancy’s breeding limit (it differs for every cat), no more special offspring could ever be produced, giving them an increased rarity appeal.

Purrstige Cats

Purrstige cats are those that have special, time-limited cattributes that can be bred based on a recipe of genes. This recipe is secret and is not known beforehand, meaning that a player needs the right combination of cattributes and hidden genes in the two-parent cats.

It’s important to remember that these traits are only breedable for a limited amount of time, which makes breeding these traits challenging. However, the rewards can more than exceed the effort, with many pointing out that purrstige traits create the game’s most beautiful and visually appealing cats.

What You Need to Get Started

Now that you have a basic understanding of CryptoKitties’ premise and characters, we can review what each player will need if they want to get started buying and selling Kitties. Those who want to participate in the marketplace will need to create a CryptoKitties account, as well as have an Ethereum wallet to store tokens. As MetaMask is the most popular wallet to store Ethereum today, it remains the top choice for most players.

Downloading MetaMask

To download and install MetaMask, navigate to the wallet’s official site found here.

Once at the site, click “Download Now” and then select the platform you want to download from.

After that, follow the installation steps.

Lastly, you will want to transfer some Ethereum into your MetaMask wallet. This can be accomplished by going to a major cryptocurrency exchange, such as Coinbase, and purchasing ETH with a bank or credit card. This ETH can then easily be transferred to your MetaMask by using your QR code or by copying and pasting your MetaMask wallet address.

Creating An Account

To create an account, navigate to the CryptoKitties website found here, and follow the steps below.

  1. You will first need to click on the “Start” button in the top right-hand corner of the homepage.
  2. Next, a MetaMask popup box will ask you to sign in to CryptoKitties. Click on Sign In.
  3. After connecting your wallet, you will need to enter your email address and choose a nickname.
  4. You will now be shown the CryptoKitties terms and conditions. After you have read through the terms, click “Agree.”
  5. You should now be fully connected to the CryptoKitties platform, which means you can buy and sell Kitties!

Buying Kitties

The fun part begins now that you have a MetaMask wallet that is funded with ETH and a registered account. To buy your first CryptoKitty, follow the steps below:

  1. Click on the ‘Search’ button at the top of the page and scroll down to the “For Sale” button. This shows every cat that is available to buy.
  2. Be sure to use the various filters such as ‘price,’ ‘mint,’ and ‘sire’ to narrow down your results as there are currently over 168,000 cats available to buy! As of the writing of this article, the cheapest CryptoKitty for sale is priced at 0.005 ETH, with the most expensive priced at over 310 trillion ETH.
  3. Click on the picture of the Kitty when you have identified one that you want to purchase.
  4. Then click on the orange ‘Buy Now’ button.
  5. Before the trade is completed, you will need to confirm the amount. Once you are happy, click on ‘OK, buy this Kitty.
  6. A MetaMask pop-up will appear showing the details of the transaction, along with the gas fees for the deal. If you are satisfied, click on ‘Confirmto complete the trade.

Once the Ethereum blockchain processes the transaction after a few minutes, the NFT will be displayed in your MetaMask wallet.


It’s also important to note that players can buy CryptoKitties on Opensea through FLOLiO. While Kitties bought on OpenSea will show up in your wallet in the same way that marketplace NFTs will, many prefer to use the actual CryptoKitties marketplace for its easy-to-use interface.

Breeding Kitties

While breeding Kitties may seem like a complicated process, there are only two ways to make it happen – breeding two kitties together that you own, or using a public sire.

The first of these methods is by far the most common. To breed two Kitties you own together, simply click on one of them in your litter, and then click the “Breed” button; this will be the Sire. Then click on “Sire with my Kitties,” and pick a cat to act as Dame; hit “OK, give them some privacy” to open up a transaction window, and soon you’ll have your own egg.

To breed with a public sire, go to “Search,” then “Siring,” and choose the Kitty you want to be the father. Keep in mind that while certain cats can Sire for free, there will still be a small transaction fee associated with the process.

Generation Number

One important trait to keep in mind when breeding Kitties is generation number. The generation number tells a player how many generations a cat is removed from the Gen 0 kitties, which are introduced into the game every 15 minutes and are the most coveted of any generation.

As a rule of thumb, the lower the Generation, the more expensive the Siring fee will be. The higher the generation number, the worse the kitty will perform, giving it a lower value.

Considering this, the best practice is to breed two Kitties of the same generation, since the offspring’s generation will be the highest generation of both parents plus one.

For example, if you breed a Gen 3 and a Gen 4 Kitty together, you get a Gen 5 Kitty. If a Gen 0 kitty breeds with another Gen 0 kitty, the offspring will be Gen 1.


In normal CryptoKitties, genes are classified as either primary or hidden based on their location in the Kitty’s genome sequence. This is important because a primary trait has a 75% chance of getting passed on, while a hidden gene only has a 25% chance of being inherited.

To get technical, every Kitty’s genome is made up of a string of blocks, each containing four genes. Every block of four represents one trait: eyes, fur pattern, body-color, et cetera. Each block has one primary gene and three hidden genes. While the hidden traits aren’t visible in a cat’s appearance, they may get inherited by its offspring.


There often occurs cases in breeding where a newborn cat will possess a trait not seen in either of its parents. This is not a glitch in the game but arises as a result of a mutation in the breeding process. Like in real biology, this new gene will be able to be passed down to the cat’s offspring.

Kitty Calculator

Breeders are keenly interested in genes because studying a cat’s genetic makeup allows players to predict what offspring may look like. While a breeder will never know with 100% accuracy, certain traits can be created by breeding the right mother and father.

Luckily, there are breeding calculators for those who don’t have time to dive into every trait of two parents. There are both official and unofficial calculators, so choose wisely before using a calculator from the internet.

Cooldown Speed

The time that a Kitty needs to rest after it breeds is called the cooldown speed. Contrary to popular belief, cooldown speed has nothing to do with a cat’s genes but is purely linked to a Kittie’s generation number.

Cooldown speed is measured on a scale from “fast” to “catatonic,” with cats that can breed faster being more desirable.

Generally, the more offspring a Kitty has, the longer it needs to rest between breedings. And every time a Kitty breeds, its next cooldown period lasts longer.

Selling Kitties

To sell a Kitty, whether to make money or simply because you want a change, simply navigate to your litter and click on the cat you wish to sell. Next, click on the “Sell” button, which will create a sale auction. Sellers have the option to pick the starting price, the ending price, and the duration of the auction.

Once an auction is listed, other players can find your sale auction on the marketplace.

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