What size is a United Kingdom visa photo?

35 × 45 mm (1.38 × 1.77 in). A digital file is 600 × 750 px.

Can I take a United Kingdom visa photo with my phone?

Yes. PhotoSpec crops to 35 × 45 mm and checks the framing before you save. Photos are processed on the phone and are not uploaded.

United Kingdom

35 × 45 mm · 600 × 750 px · Up to 6 MB

Photo size	35 × 45 mm (1.38 × 1.77 in)
Head height	64–76% of the photo height
Background	A light-coloured background is required. The authority does not name a specific colour.
Digital size	600 × 750 px, up to 6 MB
File format	jpeg
Retouching	Not allowed. The photo must not be digitally altered beyond cropping.
Background replacement	Not allowed. Shoot against a plain, evenly lit wall.
Where to take it	You can take this photo yourself.

Source: gov.uk visa photo. Rules change — check the issuing authority before you submit.

The authority allows a photo taken without a studio — its own wording is below.
you can extend your arms or ask someone to take the photo for you gov.uk

Even lighting.
be in even lighting gov.uk
Face the camera directly.
look directly at the camera gov.uk
Neutral expression.
have a neutral expression gov.uk
No filters, retouching or digital changes.
Your photo must not be altered by computer software gov.uk
Digital visa photo: do not wear glasses unless you have to.
Do not wear glasses in your photo unless you have to gov.uk

What size is a United Kingdom visa photo?: 35 × 45 mm (1.38 × 1.77 in). A digital file is 600 × 750 px.
Can I take a United Kingdom visa photo with my phone?: Yes. PhotoSpec crops to 35 × 45 mm and checks the framing before you save. Photos are processed on the phone and are not uploaded.

Passport — digital file 600×750 px, 6 MB here, 600×750 px, 10 MB there
Residence permit — same published size, background, digital file and capture rules as this document
Work permit — same published size, background, digital file and capture rules as this document

Processed on your phone. Photos are not uploaded.