To cope with the plethora of real life names for various white patterns, PKC invented its own range of names for set white patterns to make standard writing and reading easier, and UKC has also adopted these. In addition, most colours will have a "strict" and a "relaxed" range. Some breeds require the strict rules to be followed, others allow the relaxed range. If no range is listed, assume that it is "relaxed". Note that in hairless breeds white is represented by pink. However so are a lot of other colours, so bear that in mind when judging the white spotting pattern on a hairless pet.

Species similarities & differences

Cats and dogs are very similar in how they display white, but there are notable differences which, if you are familiar with one species more than another, might trip you up. Generally speaking, colour (i.e. 'not-white' fur) flows down from the top of the pet, its spine and back of the head, down the sides, and last of all going under the belly and colouring the legs and feet - almost as if someone has thrown a bucket of paint over the animal. However the details of how white behaves on each species differ:

Dogs are fairly regular creatures, their white shows up fairly evenly, any breaks in patterns are usually minor and predictable. The white fur can be ticked or roaned, but patches where present tend to be of a reasonable size and fairly soft and rounded (Dalmatian spots aren't patches, they are a modified roan and harlequin Great Danes aren't white, they are a modified Merle). Dogs tend to have higher white socks on their forelegs than their hindlegs.

Cats are also fairly regular, but have a bit of a random factor and can throw some unusual patterns - moustaches (either white or coloured), split faces, almost complete bands of colour around a leg are not uncommon, and their patches can be large or small, rounded or irregular. However when their fur is white, it is never roaned or ticked. Unlike dogs, they actually tend to have higher white socks on their hindlegs than their forelegs.

Sleeves

Both cats and dogs may have sleeves; a sleeve is when an animal has an almost solid coloured leg in an otherwise higher degree white pattern such as piebald/harlequin.
The following guidelines exist on sleeves:

One sleeve "per animal" is allowed. Having two coloured sleeves on a high degree white animal is just too rare/unrealistic.
The toes/fingers must still be white on the leg with the sleeve
The sleeve should be attached to a body patch of some sort

Canine patterns

Dogs have traditionally been grouped into a few basic white patterns which may be known under different names depending on breed. The exact genetic background of these patterns is not known at this time and at times they may overlap each other. There can always be exceptions to the recommendations and rules listed below. It's impossible to cater to all possible combinations and random occurences that can happen in real life. UKC's white spotting requirements are based on PKC's requirements and research as to what is reasonably typical and realistic in the average real life population, adapted to petz as well as is possible.

NOTE - check individual standards for exceptions to these rules.

Dogs have four main patterns; White Trim, Irish Spotting, Piebald and Extreme White. As certain appearances are bred for in some breeds, there are two modified patterns also - Strict Irish Spotting (where a precise Irish Spotting pattern is required) and Blanket (which is either a particularly heavy form of Piebald or a light form of Irish Spotting, depending on the perspective of the breed). Unless a breed standard specifically requires one or more of these modified patterns, you can assume anywhere in the range between minimum and maximum is acceptable. Small disruptions to the pattern such as a small degree of asymmetry, or a small patch of colour within an optional white area are allowed in all patterns by default. Small patches of colour within non-optional white areas (i.e. those listed as minimum requirements) are only allowed if specifically stated.

White trim

White trim is the smallest amount of white possible in dogs and consists of one, several or all of the following white markings:

chest patch. If a chest patch is present, there may also be white on the front of the throat, either as a separate patch or connected to the chest patch.
toes
fingers
chin
jowls
spot and/or blaze on head and/or muzzle
tailtip

Irish Spotting, Piebald and Extreme White

The following are guidelines for dogz with more white than trim. For more exact guidelines on head markings, see further below.
Note: The examples given for the are just that - examples. They do not represent the only way to pattern a dog, just examples of how dogs range from mid-to-high white, and from more solid to more broken patterns.

Pattern	Irish Spotting	Piebald (incl. Blanket)	Extreme White
Description	Predominantly coloured with white on the extremities and forequarters (~30%).	Predominantly white (up to ~75%). Coloured fur may be present as patches or forming a blanket. If the standard says 'Piebald' the markings can be arranged as patches or as a blanket. If it only says 'Blanket' then only blanket markings are allowed.	Predominantly white (~75%+) (must have at least one visible patch of colour). Colour normally confined to the head and/or root of tail, but a few body patches may occur.
Minimum white requirements	White toes/fingers on all four feet, chest patch, tailtip.	The front of chest, feet and legs and tailtip. Additional white markings must also be present.	The front of chest, feet and legs and tailtip. Must have over 75% white. A few body patches may occur, these are normally be confined to the head, upper body and/or tail/rump areas.
Maximum white requirements	White muzzle and blaze, collar, chest (may include whole frontlegs), underside of belly (if present requires large chest patch), feet and lower legs, tailtip.	Up to 75% white. Regardless of where else it occurs, colour must be present on at least either one ear base and/or base of tail.	Solid white with a single patch on at least one ear base and/or base of tail.
Small coloured patches allowed to disrupt the minimum required white on the:*	Chest patch	Legs	None
White allowed on the ears:	No	Yes	Yes
Variation spectrum (a few typical examples)

* This row only covers whether the white listed in 'Minimum white requirements' can be patched. With regards to the rest of the white on the dog, a patch infringing a white marking, or a small patch complete within a white area are acceptable as long as the pattern is not excessively disrupted as a result.

More examples of these white patterns and how they look on dogz of different breeds, files and patterns are available on all of the other standard definitions pages. The white pattern present on each example is always clearly listed alongside the other patterns/markings present on the dog

Modified patterns

Irish Spotting (strict)

If a breed standard lists Irish spotting (strict) the white pattern must be as follows: white muzzle, neck, chest, feet, lower legs (hind legs may have white toes only), tailtip. A blaze is preferred, may have a full or partial neck collar. White undersides optional. Symmetrical markings preferred.

Blanket

Blanket is a specific form of Piebald. Therefore it follows the same rules as Piebald except the colour on the body is present as a blanket rather than broken patches. Unless stated on the standard, the blanket may be broken by a few small spots or stripes of white without fault. Mostly symmetrical markings preferred, but a small degree of asymmetry is acceptable.

White head markings

Generally speaking, a high-white dog may have either a predominately white or a predominately coloured head, however a low-white dog will normally have a predominately coloured head. There are exceptions to this rule, which are always listed in the individual breed standard (e.g. coloured heads in high whites are more common in Gundog breeds, while white heads in low-whites are more common in Bully breeds). White fully surrounding the eyes are a DQ in many breeds in RL, so refer to the breed standard before hexing such patterns.

White on the ears in dogs will begin at the tips and reach the base last. Therefore, a coloured ear with a white tip is realistic, while a coloured tip with a white base is not.

For all of the below, a small area or areas of colour may occur on an otherwise white area, such as a spot of colour on the muzzle. Such markings would normally be considered undesirable in breeds with stricter standards. In breeds with looser standards, they may be accepted without fault.

Type of Marking	White Trim	Irish Spotting	Piebald	Extreme White
Solid coloured head	Yes	Relaxed only	Yes	Yes (but not typical)
Blazes, spots	Yes	Relaxed only	Yes	Yes
Lower degrees of white on the muzzle	Yes	Relaxed only	Yes	Yes
White muzzle and blaze	No	Yes	Yes	Yes
White muzzle, wide blaze, white surrounding eyes; more than 50 % white on head in total	No	No	Yes in Piebalds, but only allowed on Blankets if breed also allows Piebald	Yes
White on eartips (symmetrical or asymmetrical)	No	No	Yes in Piebalds, but only allowed on Blankets if breed also allows Piebald	Yes
White head with coloured ear bases; ears can be coloured, partially or fully white, and markings can be symmetrical or asymmetrical	No	No	Yes in Piebalds, but only allowed on Blankets if breed also allows Piebald	Yes
'Split face' type markings; one or two fully white ears with patch/es on skull	No	No	Yes in Piebalds, but only allowed on Blankets if breed also allows Piebald	Yes
Solid white head	No	No	No	Yes