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GEMS Codes

A Guide to GEMS – the GCCF Easy Mind System

The EMS cat breed codes were developed by Dagny Dickens of Sweden and Eva Minde of Norway.  They were introduced by FIFe (Federation International Feline d’Europe) to describe all breeds, colours and patterns without too much complication.  The GCCF has adopted EMS, however, differences between GCCF and FIFe required changes that resulted in GEMS (GCCF EMS) codes being developed.  The two systems are very similar and it is likely that eventually GEMS will be one of several compatible versions of EMS.

You can download the GEMS codes here.

GEMS Code Structure

GEMS (and EMS) codes consist of a number of elements separated by spaces; breed, colour and numerical codes (for any other characteristics).  GEMS codes may also have a variant indication after the numerical codes.  Only the breed part is mandatory, the other elements may or may not be required to describe the cat.  Many cats can be described with just four characters and few require more than a dozen.

The Codes for Breeds

The first part of the EMS code denotes the cat’s breed and consists of three upper case letters such as BUR (Burmese), MCO (Maine Coon), SIA (Siamese) etc.  If the breed comes in both short-haired and long-haired varieties, its code will end with S (or SH) or L (or LH) to denote the different coat lengths (LPL = LaPerm Longhair; OSH = Oriental Shorthair etc).

Coat Colours

A cat’s colour may be described using one or more lower case letters to indicate the basic colour such as “a” (blue), “d” (red) etc. along with additional lower case letters for silver, golden or, in the case of Norwegian Forest Cats, amber.

Numerical Codes

Numbers are used to give information that is specific to some cats.  The numerical codes indicate whether a cat has white; tipping or shading; a tabby pattern; a particular colour restriction or an eye colour that affects its breed class.  In addition there are a few numerical codes that are breed specific such as Manx tail codes or Ragdoll mitting.


The code “v” is added to the end of a cat’s GEMS code sequence to indicate a variant. Variants may not be shown competitively in their own breed classes.  They may be eligible for showing in another breed’s classes if they have a Show Code.

Show Codes

Show codes are only required for variants of a breed that have the genotype of an existing breed and are allowed to be shown in this other breed’s show classes.  Such variants have two GEMS codes; the first gives genotype and breed description as defined via their registration policy followed by the second, the show code, which is simply another GEMS code in brackets thus () designating phenotype – what the cat ‘looks like’ – and hence show class.

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