- White must predominate with black and/or tan markings.
- The tan markings can be from the lightest tan to the richest tan (chestnut)
Small, energetic earth-working terrier with a predominantly white coat and sturdy build, known for its bold, athletic nature and lively temperament, originally bred for fox hunting
Developed in southern England during the mid-1800s by Reverend John Russell for fox hunting, bred to bolt foxes from dens. The shorter-legged variety standard was primarily developed in Australia.
“A lively, alert and active Terrier with a keen, intelligent expression. Bold and fearless, friendly but quietly confident”
Quoted from FCI standard n°345. It describes the breed the registry recognises, not any individual animal.
Breed reference from The Dog API.
Drawn from sources, not opinion: FCI breed standard; UC Davis Veterinary Genetics Laboratory — Primary Lens Luxation. An empty column means we hold nothing for that side, not that there is nothing to say.
The Jack Russell Terrier standard is published by the FCI (Fédération Cynologique Internationale), the international federation of pedigree-dog clubs, and it is what show judges apply. This section sums up what it says about coat and colour and size. It does not assess any one animal: use it to know what to ask the breeder.
May be smooth, broken or rough.
Must be weatherproof.
Coats should not be altered (stripped out) to appear smooth or broken
Shortened from FCI standard n°345 — each label is the standard’s own wording with the verdict lifted into the tag beside it. Read the full clause at source.
The colours and patterns the standard admits, and what it prefers, discourages or disqualifies in each. An accepted colour says nothing about health.
Quoted from FCI standard n°345. It describes the breed the registry recognises, not any individual animal.
An adult's measurements, per the standard. It does not say how big this puppy will be. Quotations from the FCI are in English, as the standard publishes them; the headings are ours.
Breed-level information from The Dog API. It describes the Jack Russell Terrier in general; any individual animal can differ.
Known hereditary risks for the Jack Russell Terrier breed, and the specific documentation to request from any breeder before paying a deposit. A responsible breeder will have these readily available; deflection is a red flag.
9 conditions documentedThis is breed-level literature, not veterinary advice about an individual animal — your vet knows the animal.
Health checklist (PDF)Documented in this breed, but no source says how many of its dogs carry or have them. That is a gap in the evidence, not a sign they are rare.
A juvenile-onset neurological disease (KCNJ10 gene) causing progressive incoordination from as young as 2 months old, often with muscle twitching (myokymia) and seizure-like episodes; affected dogs are usually euthanised before 3 to 4 years old because of declining quality of life. Documented directly in Jack Russell Terriers, not inferred from a related breed.
What to ask for
DNA test result for the KCNJ10 mutation on both parents, sold as 'spinocerebellar ataxia, terrier type' by Paw Print Genetics/Orivet, Laboklin, Canine Genetic Testing (CAGT) and others.
The lens of the eye detaches from its normal supporting fibres, usually between 3 and 8 years old; it is painful, can cause secondary glaucoma, and is usually treated as a same-day surgical emergency. The causative ADAMTS17 mutation was first identified in this breed (together with the Lancashire Heeler and Miniature Bull Terrier).
What to ask for
DNA test result for the ADAMTS17 primary lens luxation mutation on both parents — part of the UK Kennel Club's official testing scheme, and also offered by UC Davis VGL, Laboklin and other laboratories.
A juvenile-onset neurological disease (KCNJ10 gene) causing progressive incoordination from as young as 2 months old, often with muscle twitching (myokymia) and seizure-like episodes; affected dogs are usually euthanised before 3 to 4 years old because of declining quality of life. Documented directly in Jack Russell Terriers, not inferred from a related breed.
What to ask for
DNA test result for the KCNJ10 mutation on both parents, sold as 'spinocerebellar ataxia, terrier type' by Paw Print Genetics/Orivet, Laboklin, Canine Genetic Testing (CAGT) and others.
The lens of the eye detaches from its normal supporting fibres, usually between 3 and 8 years old; it is painful, can cause secondary glaucoma, and is usually treated as a same-day surgical emergency. The causative ADAMTS17 mutation was first identified in this breed (together with the Lancashire Heeler and Miniature Bull Terrier).
What to ask for
DNA test result for the ADAMTS17 primary lens luxation mutation on both parents — part of the UK Kennel Club's official testing scheme, and also offered by UC Davis VGL, Laboklin and other laboratories.
Found in roughly one in a hundred to one in twenty of the breed's dogs screened.
An inherited degeneration of the retina that starts as night blindness in adulthood and slowly progresses to blindness; there is no treatment. It is recessive. It is uncommon in this breed — roughly one in 80 of 239 Jack Russells screened carried it.
What to ask for
DNA test for prcd-PRA on both parents
An inherited high level of uric acid in the urine (SLC2A9 gene) that makes urate bladder and kidney stones likely; a stone blocking a male dog's urethra is an emergency. It is recessive. It is uncommon in this breed — roughly one in 80 of 239 Jack Russells screened carried it. Once known, it can be managed with diet and monitoring.
What to ask for
Hyperuricosuria (SLC2A9) DNA test result, on both parents
Deafness present from birth in one or both ears, associated with the breed's predominantly white coat pattern; it does not progress or improve and has no treatment. The parent club treats it as a genetic issue to be bred away from, not an individual misfortune. In BAER testing of 1,009 Jack Russell Terriers in the US, about one in 28 was deaf in one ear and one in 200 in both, lower than earlier reports from smaller groups of related dogs; deafness was commoner in dogs with more white and in pups of deaf parents.
What to ask for
Not a DNA test — a BAER (brainstem auditory evoked response) hearing-test result on the individual dog, performed after 5 weeks of age, per the Jack Russell Terrier Club of America's protocol. Ask whether the breeding stock and the litter itself were BAER tested.
An inherited degeneration of the retina that starts as night blindness in adulthood and slowly progresses to blindness; there is no treatment. It is recessive. It is uncommon in this breed — roughly one in 80 of 239 Jack Russells screened carried it.
What to ask for
DNA test for prcd-PRA on both parents
Described in this breed, but found in few or no dogs in recent screening, or only ever in one dog or one family. They are here so a test result makes sense if a breeder mentions one.
An inherited disease of the cerebellum and spinal cord described in the closely related Parson Russell Terrier: signs usually appear between six and twelve months old, with progressive unsteadiness, especially of the hind legs, and loss of balance, and later many dogs can hardly walk. It is recessive. The variant is listed for this breed too, but none of 239 Jack Russells in a recent screen carried it, against roughly one in eight Parson Russells.
What to ask for
Spinocerebellar ataxia (CAPN1, late-onset ataxia) DNA test result, on both parents
An inherited weakness at the junction between nerve and muscle, and the first congenital myasthenic syndrome recognised in dogs, in this breed in 1974: young affected dogs tire quickly with exercise. It is recessive. Its CHRNE variant was confirmed in two recent littermates and in tissue kept from the 1970s cases; none of 239 Jack Russells in a recent screen carried it.
What to ask for
Congenital myasthenic syndrome (CHRNE, Jack Russell type) DNA test result, on both parents
An inherited failure of the immune system described in a litter of this breed: affected puppies cannot make working lymphocytes, so they have almost no defence against infection. It is recessive. Fewer than one Jack Russell in ninety carried it when it was studied, and none of 239 did in a recent screen.
What to ask for
Severe combined immunodeficiency (PRKDC, Jack Russell type) DNA test result, on both parents
An inherited, severe scaling of the whole skin described in this breed: affected puppies' skin is covered in thick scale, and in a recent litter the affected puppies were underweight, got worse and were put to sleep. It is recessive. None of 238 Jack Russells in a recent screen carried it.
What to ask for
Lamellar ichthyosis (TGM1, Jack Russell type) DNA test result, on both parents
An inherited disease of the cerebellum and spinal cord described in the closely related Parson Russell Terrier: signs usually appear between six and twelve months old, with progressive unsteadiness, especially of the hind legs, and loss of balance, and later many dogs can hardly walk. It is recessive. The variant is listed for this breed too, but none of 239 Jack Russells in a recent screen carried it, against roughly one in eight Parson Russells.
What to ask for
Spinocerebellar ataxia (CAPN1, late-onset ataxia) DNA test result, on both parents
Median survival 13.3 years
95% confidence interval 13.2–13.3 years, from 13,497 recorded deaths among 19,177 dogs
Mortality hazard 0.79 (0.77, 0.8) relative to crossbred dogs, whose median is 12.0 years.
Measured in the United Kingdom from 584,734 dogs. Median survival is not a prediction for an individual dog.
McMillan, K.M., Bielby, J., Williams, C.L., Upjohn, M.M., Casey, R.A. & Christley, R.M. (2024) Longevity of companion dog breeds: those at risk from early death. Scientific Reports 14, 531.
Deafness present from birth in one or both ears, associated with the breed's predominantly white coat pattern; it does not progress or improve and has no treatment. The parent club treats it as a genetic issue to be bred away from, not an individual misfortune. In BAER testing of 1,009 Jack Russell Terriers in the US, about one in 28 was deaf in one ear and one in 200 in both, lower than earlier reports from smaller groups of related dogs; deafness was commoner in dogs with more white and in pups of deaf parents.
What to ask for
Not a DNA test — a BAER (brainstem auditory evoked response) hearing-test result on the individual dog, performed after 5 weeks of age, per the Jack Russell Terrier Club of America's protocol. Ask whether the breeding stock and the litter itself were BAER tested.
An inherited high level of uric acid in the urine (SLC2A9 gene) that makes urate bladder and kidney stones likely; a stone blocking a male dog's urethra is an emergency. It is recessive. It is uncommon in this breed — roughly one in 80 of 239 Jack Russells screened carried it. Once known, it can be managed with diet and monitoring.
What to ask for
Hyperuricosuria (SLC2A9) DNA test result, on both parents
An inherited, severe scaling of the whole skin described in this breed: affected puppies' skin is covered in thick scale, and in a recent litter the affected puppies were underweight, got worse and were put to sleep. It is recessive. None of 238 Jack Russells in a recent screen carried it.
What to ask for
Lamellar ichthyosis (TGM1, Jack Russell type) DNA test result, on both parents
An inherited weakness at the junction between nerve and muscle, and the first congenital myasthenic syndrome recognised in dogs, in this breed in 1974: young affected dogs tire quickly with exercise. It is recessive. Its CHRNE variant was confirmed in two recent littermates and in tissue kept from the 1970s cases; none of 239 Jack Russells in a recent screen carried it.
What to ask for
Congenital myasthenic syndrome (CHRNE, Jack Russell type) DNA test result, on both parents
An inherited failure of the immune system described in a litter of this breed: affected puppies cannot make working lymphocytes, so they have almost no defence against infection. It is recessive. Fewer than one Jack Russell in ninety carried it when it was studied, and none of 239 did in a recent screen.
What to ask for
Severe combined immunodeficiency (PRKDC, Jack Russell type) DNA test result, on both parents