CryptoKitties History – The Birthing Fee

Many players, both new and old alike, may not realize that the CryptoKitties birthing fee has not always been 0.008 ETH.

So here is a quick walk through the history of the birthing fee:

Nov 28, 2017: CryptoKitties launches with a birthing fee of 0.001 ETH
Dec 3, 2017: Birthing fee increased to 0.002 ETH
Dec 4, 2017: Birthing fee increased to 0.015 ETH
Dec 11, 2017: Birthing fee decreased to 0.008 ETH

Historical References

🚨🚨🚨🚨 Due to network congestion, we are increasing the birthing fee from 0.001 ETH to 0.002 ETH. This will ensure your kittens are born on time! The extra is needed to incentivize miners to add birthing txs to the chain. Long-term solution will be explored very soon! 🚨🚨🚨🚨

2:13 PM – 3 Dec 2017



1:25 PM – 4 Dec 2017

❤️❤️ We have dropped the birthing fee from 0.015 ETH to 0.008 ETH. Happy breeding everyone! 🐈

11:28 AM – 11 Dec 2017


Ralf Putmans (DerpyBastard) has graphed these birthing fee values against the ETH/USD price to chart the breeding price in USD over time (from November 28th, 2017 up through April 14th, 2018):

Birthing Fee

The average breeding price in USD over this entire time period is $6.06. Since the distribution of cats is skewed, the average amount spent to actually breed each kitty would be slightly different. You could overlay the births/day to calculate that number.

If you want to delve into the data, then please check out the Google Sheet that Derpy created:

About the Author

This article was written by Byzantinist (a.k.a. Byzantine Kitty), who is an expert on digital cat genetics. As a passionate aficionado of 100% 🐎 Purebred cats, Byzantinist runs a 🐎 Purebred Siring Shop that can be found here:

If you have any comments or feedback, you can contact me at or on Discord @Byzantinist – 🐎 Purebred Sires#2992

All About Cattributes

UPDATE: My discussion about terminology with Alanfalcon has spurred the adoption of several new terms among the CryptoKitties staff, which you might see them use in the near future. Instead of dominant (D0) and recessive genes (R1/R2/R3), they might refer to active (A0) and hidden genes (H1/H2/H3) for normal cats and H0/H1/H2/H3 for fancy cats. In addition, they prefer classifying genes found in Generation 0 cats as Level 1 while Wingtips is a Level 3 gene (instead of using the “Tier” keyword).

Every cat has a cattribute/trait in 8 different categories which each has an impact on the visual appearance of the cat (except for Fancy cats). There are also 4 additional categories which are normally hidden.

If you do not understand basic CryptoKitty genetics, including how dominant and recessive genes work, then I recommend you start with some older CryptoKitties411 articles:

The 8 primary cattribute categories are:

  • Fur / Body
  • Pattern
  • Eye Color
  • Eye Shape / Type
  • Base Color
  • Highlight / Pattern Color
  • Accent / Secondary Color
  • Mouth

One detail that is often missed is that the background of the cat image is determined by the Eye Color of the cat.

There are also 4 additional hidden categories. Basic Wild genes do not seem to do anything but Tier 1 Wild mutations (e.g. Elk, Trioculus) are additional cattributes which are displayed and impact the visual appearance of the cat. At this time, it is not known what Mystery, Secret, and Unknown genes do, though there is plenty of rampant speculation of what they might do.

Fancy cats of a given type all have the same physical appearance though the background color does change depending on Eye Color. Fancy cats are assigned a numbered Fancy badge instead of having cattributes displayed. However, they still have relevant dominant and recessive traits which can be passed down to their offspring. And while none of their family or mewtation jewels are displayed, these still exist and can be passed down as well.

Not all cattributes are the same. Some are much rarer or more valuable than others. To help you better understand the nature of cattributes, here are some broad categories that are sometimes used. Most of these terms are used colloquially (instead of there being an official definition) so there may be slight differences in meaning or usage.

Normal / Base Traits

“Normal” often means the standard traits that do not fit in any of the other categories (not mutations, retired / discontinued, or founder traits).

Sometimes, “Base” trait is used to refer to all non-mutation traits (which may include retired / discontinued and founder traits). So Jaguar might be considered a “Base” trait but not a “Normal” trait.

Founder Traits

The first 100 cats are the Founder cats and they are each assigned a special Founder badge. Every Founder cat has the following genetic makeup for their dominant and recessive genes:

Fur: Himalayan, Munchkin, Ragamuffin, or Sphynx
Pattern: All Founders are 100% 🐎 Purebred Jaguar
Eye Color: Chestnut, Mintgreen, Sizzurp, Strawberry, or Topaz
Eye Shape: Crazy, Simple, or Thicccbrowz
Base Color: All Founders are 100% 🐎 Purebred Orangesoda
Highlight Color: Chocolate, Coffee, Lemonade, Royalpurple, or Swampgreen
Accent Color: Granitegrey or Kittencream
Mouth: Beard, Happygokitty, Pouty, or Soserious

Jaguar is a special case because among Generation 0 cats it can only be found among the original 100 founders. That means that any higher generation cat with a Jaguar gene is a descendant of at least one of the Founder cats.

Beard, Chestnut, and Simple are also notable cases because the only Generation 0 cats with dominant Beard, Chestnut, or Simple are some of the Founder cats. These genes may appear in non-Founder Generation 0 cats but only as recessive genes.

The traits listed above are collectively called Founder traits because they were present in those original cats. However, these genes can be found in other Generation 0 cats as well (except no Beard, Chestnut, or Simple as dominant and no Jaguar at all).

Since jewels were introduced much later, Founder traits are also notable because they do not have associated jewels (no diamond, gild, amethyst, or lapis). This can be an important consideration for players who want 8 jewel or 9 jewel cats.

There are also some additional jewel-less traits that are often considered Founder traits even though none of the 100 Founder cats technically had any of these genes:

Pattern: Luckystripe, Totesbasic F, and Totesbasic G
Base Color: Aquamarine, Greymatter, Salmon, and Shadowgrey

These cattributes can be found in some of the earliest cats (e.g. Bug Cat exclusive, 500-number cats) and other low number cats (e.g. Knight Kitty exclusives).

Retired / Discontinued Traits

Over time, some traits are phased out and no longer appear in new Generation 0 cats. These are referred to as “Retired” or “Discontinued” traits. Note that this is not an official designation. There is nothing to prevent Axiom Zen from including these genes again in upcoming Generation 0 cats but that has not happened so far.

An older list of Discontinued traits can be found here:

Discontinued Traits

I do plan to write an article in the near future to update the list of Retired / Discontinued Traits.

“Recessive” Traits

Recessive traits (which is different than recessive genes) is sometimes used to refer to traits that show up in recessive positions (R1, R2, or R3) in Generation 0 cats but are not expressed (D0) in any of those cats. The only way for these genes to become dominant is to breed the cats until gene swapping causes them to move into the D0 position.

The following traits can be found as recessive genes but not dominant in Generation 0 cats:

Fur: Chartreux and Savannah
Pattern: Calicool, Camo, Ganado, and Spock
Eye Color: Doridnudibranch and Forgetmenot
Eye Shape: Baddate, Otaku, Serpent, and Stunned
Base Color: Dragonfruit, Harbourfog, Hintomint, and Nachocheez
Highlight Color: Apricot, Barkbrown, Lilac, Poisonberry, Scarlet, Springcrocus, and Violet
Accent Color: Belleblue, Emeraldgreen, Missmuffet, and Peach
Mouth: Belch, Gerbil, Wasntme, and Whixtensions

Since it requires gene swapping to get these traits into a dominant position, it is rarer to see these cattributes expressed among low generation cats.

Furthermore, some recessive traits are rarer than others. For example, Chartreux can only be found in the R3 position of Generation 0 cats while Camo can be found in R2 or R3, and Otaku can be found in R1, R2, or R3.

As a result, for Generation 1 cats, a Chartreux is rarer than a Camo, which is rarer than an Otaku, which is rarer than a normal trait like Totesbasic or Granitegrey.

I will be going into more depth on these recessive traits in an upcoming article.

Mutation Traits

When two cats breed, certain pairs of traits can mutate into a new trait. For a primer on mutations, please take a look here:


Mutation traits simply do not appear in Generation 0 cats as dominant or recessive genes. So if you see something like this:

You know there is something wrong because Tigerpunk is a mutation and Otaku is a recessive trait so neither should be dominant in a Gen 0 cat. If you actually look at this cat’s genetic code, you will see that its Pattern is really Totesbasic F and its Eye Type is Thicccbrowz. So this is a front-end bug with the website.

It takes time for mutations to propagate so low generation cats with mutations can be extremely valuable and 🐎 Purebreds are not even possible until several generations have passed.

Note that there is some variance with terminology. Most people seem to refer to Cloudwhite as a Tier 1 mutation and Wingtips as a Tier 2 mutation. However, there are some people who refer to all base traits (non-mutations) as Tier 1, which would make Cloudwhite Tier 2 and Wingtips Tier 3. Furthermore, Alanfalcon has been advocating the use of “ascension” instead of “mutation.”

About the Author

This article was written by Byzantinist (a.k.a. Byzantine Kitty), who is an expert on digital cat genetics. As a passionate aficionado of 100% 🐎 Purebred cats, Byzantinist runs a 🐎 Purebred Siring Shop that can be found here:

If you have any comments or feedback, you can contact me at or on Discord @Byzantinist – 🐎 Purebred Sires#2992


Original Artwork

There have been a few instances where the developers have changed the artwork on certain traits. It can be assumed that cats with the original artwork will never be able to be reproduced (which would make them more rare). Do you have an original?

Serpent – original artwork has thinner upper eyelids

  • Last kitty with original artwork: 456675
  • First kitty with new artwork: 456709
  • Total OG serpents: 3,346

OG serpent

Onyx – original artwork has black whiskers instead of white

  • Last kitty with original artwork: 478686
  • First kitty with new artwork: 478762
  • Total OG onyx: 380

OG onyx

Pouty – original artwork had a slight smile

  • Last kitty with original artwork: 478717
  • First kitty with new artwork: 478733
  • Total OG pouty: 95,980

OG pouty

Ganado – original artwork had diamonds that matched the side and chest colors

  • Last kitty with original artwork: 483035
  • First kitty with new artwork: 483066
  • Total OG ganado: 11

OG ganado

Frosting – original artwork was the exact same shade of pink as azaleablush

  • Last kitty with original artwork: 663425
  • First kitty with new artwork: 663451
  • Total OG frosting: 84

og frosting.PNG


Happy Collecting!
– Jodiferous

See related post: What’s Rare? What’s Desirable?

ck banner 3

Breeding Calculators

When you’re breeding cats, it’s nice to know what traits are likely to be passed on to offspring. It helps you make better decisions.

When CryptoKitties started getting popular, a lot of people started making “breeding calculators” even though the cats’ genetics weren’t fully understood. These calculators relied on anything from guessing to machine learning, but basically all of them were inaccurate to some degree.

Now that the genetics have been cracked and the smart contract analyzed, it’s possible to have breeding calculators that are exact and accurate. But a lot of the incorrect calculators still exist on the web!

There are, however, a few really good calculators. I really like and KittyAppX.

KittyCalc shows the breeding outcomes visually in a donut chart and also rates the traits on attractiveness (subjectively, of course). It also specifies which traits may appear as a result of mutation.

kittycalc pic

The interesting thing about KittyCalc is that it was created by players who not only understand the true math behind the breeding algorithm but are artists as well. As a result, they’ve incorporated suggestions on what traits pair well together.

They did, however, get one detail embarrassingly wrong. “Thicccbrowz” is a FIVE-STAR trait, you guys!! What are you thinking??

Pfff. Cookie and I are deeply offended.


What’s Rare? What’s Desirable?

What makes some CryptoKitties more valuable than others? Why do some kitties plummet in value while others don’t? How can you tell ahead of time?

Kitties get their value from two things: RARITY and DESIRABILITY. If a cat can maintain both over time, it’ll hold its value much better than the new hotshot cat with shiny antlers. Here are some things to think about before buying the expensive kitty in the window.


Gen 0 Cats

There will only be 50,000 Gen 0 cats, and they will no longer be produced after November 2018. Other generations can be created through breeding, but Gen 0 cats cannot. They will be more scarce than higher generations.Read More »


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 »

Breeding Outcomes

Dominant and Recessive Genes

Unlike traditional genetics, where dominant and recessive genes have to do with the traits themselves (e.g. blond hair is recessive to black hair), CryptoKitty genes are dominant and recessive based on where they are located in the kitty’s genome, and it affects what gets passed to offspring.Read More »