How to take a UK passport digital photo with your phone
This is the one document on the site with nothing to print. The online passport application takes either a digital code from a booth or a shop, or a photo you take yourself with your own device and upload — and the second route is why the file requirements are written in pixels rather than millimetres: at least 600 pixels wide and 750 tall, JPEG, between 50 KB and 10 MB. Any modern phone clears that with room to spare; the risk is the other direction, sending a heavily compressed copy pulled out of a chat app.
The framing still follows the printed photo: a 36×45 mm proportion with the head 29–34 mm from the crown to the chin. Have someone hold the phone at your eye level with the rear camera, about 1.5 metres from a plain light wall, and leave space around you — the upload will be cropped, and space is the only thing you cannot add later. Do not edit the result. The photo has to be unaltered by software, which rules out the beauty filters some phones apply by default, so turn those off before the first shot.
Why a UK passport digital photo comes back
The background must be plain and light with clear contrast against your face, and free of shadows — the single most common rejection is a shadow cast onto the wall behind the head.
The photo must be taken within the last month, which is far stricter than the six months most countries allow, so a picture from the summer will not do in the autumn. Glasses should come off unless you have to wear them, and even then the eyes must not be obscured by frames or glare. Also refused: sunglasses and tinted lenses, red eye, hair across the eyes, anything covering the face, a head covering worn for reasons other than religious or medical ones, and any other person or object in the frame. The expression is plain with the mouth closed, looking straight into the lens.
Where a UK passport digital photo is used
It covers the online application for a first passport, a renewal and a child's passport, and once accepted it is checked on submission rather than weeks later. Keep the file: the same picture is what a replacement or an urgent application will ask for. The current rules are on the official gov.uk passport photo page.