Before reading this post, you should know how to read a kitty’s genes.

Each trait in CryptoKitties has a “mutation pair” that, when bred together, gives a small chance (usually 14%) of generating a brand new trait not necessarily seen in either parent. Those new traits are referred to as mutations. After a gene mutates, it may then be passed on to offspring the same way as basic traits.

Because Gen 0 cats only have basic traits, mutations tend to be rare at low generations, so they are often (but not always) more valuable.

(Note: Mutations are separate from the “recessive” genes that have a chance to gene swap into the dominant position.)

How do mutations work?

From a technical point-of-view, mutations occur when pairs of neighboring genes (e.g. 00010 & 00011) are bred together. If they mutate, the mutation takes the gene with a ‘1’ at the end and moves it to the beginning (e.g. 00011 –> 10001). You don’t really need to know that, though. You can just use the following method.

In the chart below, you can see that topaz and mintgreen are a neighboring pair. In the right-hand column, it says they mutate into gene ‘i’. Find ‘i’ in the kai column and trace it back to eye color. Topaz and mintgreen have the potential to mutate into limegreen.

To find all possible mutations, please see our updated Trait Chart.

ck kai chart mutations red.png
What are the odds of mutation?

Read More »

How to Breed Cats Using the Smart Contract (MEW)

Cats being stuck with “Bun in Oven” or “Resting” is a common issue, and it will generally resolve itself within a few hours. But in case you don’t want to wait, you can call the smart contract manually using MyEtherWallet.

Breeding with Smart Contract (MEW)

UPDATE: They have removed the CryptoKitties contract from MEW. You can copy the ABI from here:

STEP 0: Make sure your cats are ready to breed or the transaction will fail. (Click on the link in step 3 and enter the kitty IDs individually on line 29 “isReadyToBreed” and click on Query to check.)

1. Go to
2. Click on the Contracts tab.
3. Select the CryptoKitties smart contract (the address should match
4. Click Access.
5. Select the breedWithAuto function.
6. Input the kitty IDs of your matron and sire.
7. Select Metamask as your sending option in the bottom. Click Connect to Metamask.
8. Press Write and enter in the breeding fee (currently 0.008 at the time of this post, this breeding fee can change) as the sending value in the popup.
9. Send the transaction and in the Metamask popup, enter your gas price. (See for current gas prices.)

Once your transaction is successful, the matron of the breeding pair should have a new Bun in the Oven. Happy breeding!

Here is a video walk-through of the process provided by LucyintheSky:

breed with MEW 1

breed with MEW 2

breed with MEW 3

Courtesy of DERPYBASTARD and anyone else who contributed to this how-to guide.