Why this page is split in two
The UK requirements are a mixture of two very different kinds of rule. Some are numbers: 600 × 750 pixels minimum, between 50 KB and 10 MB, in colour. A photograph either satisfies those or it does not, and a tool that says so is reporting a fact.
The rest are descriptions: “plain light-coloured background”, “clear and in focus”, “no shadows”. No threshold is published for any of them, because the check is performed by a person. Any tool that gives you a green tick for “background: acceptable” has invented a cutoff and is presenting its own guess with the authority of the Passport Office behind it.
So this checker measures both, and keeps them apart on screen. Failing an official check means your application will be refused. Failing one of ours means we think a human would object, and we show you the number we based that on so you can disagree.
What is measured, and how
From the published requirements
| Check | Method |
|---|---|
| Pixel dimensions | Compared against the published minimum of 600 × 750 px. |
| File size | Compared against the 50 KB floor and the 10 MB ceiling. The floor catches people out. |
| In colour | Measured as the spread between the red, green and blue channels. A greyscale photo scores zero. |
Our own thresholds
| Check | Method |
|---|---|
| Focus | Edge energy across a 512-pixel crop from the middle of the frame, at full resolution — measuring a shrunken copy would hide the blur. |
| Exposure | The share of pixels crushed to pure black or blown to pure white, where no detail survives. |
| Background is light | Mean brightness across the top band of the frame, where the wall is and your shoulders are not. |
| Background is plain | Variation within that band. A door frame, a picture edge, patterned wallpaper and a curtain all raise it. |
| No shadow across the background | The difference between the left and right thirds of the band. A side light shows up as a tilt. |
Every one of those thresholds has a test behind it. A flat light wall must keep passing “background is plain”, a patterned one must keep failing it, and a smooth gradient must not be mistaken for a sharp photograph — that last one being the case where a naive implementation, measuring contrast rather than edges, gets it exactly backwards.
The check that matters most is not on this page
The commonest geometric reason a UK application is refused is that the head is the wrong size in the frame. It must measure between 29 mm and 34 mm from the bottom of the chin to the crown, inside a 45 mm photograph — a window of 5 millimetres.
Automatic face detection cannot answer that reliably, and the reason is specific: it finds the top of the hair, and the rule is about the top of the skull. On anyone with volume in their hair the difference is several millimetres — a large share of the permitted window — and the error is invisible, because the box looks right. Rather than report a confident number that is quietly wrong, the passport photo tool asks you to place two marks and computes everything from them.
Verified against the source
The published numbers on this page were re-read on 2026-08-11 from GOV.UK — Get a passport photo . Requirements change; check the official page before you submit, and treat this checker as a second pair of eyes rather than a decision.
Frequently asked questions
Is this the official checker?
No, and nothing is. HM Passport Office does not publish a checker, and no third-party tool can commit them to accepting a photo. What this page does is measure the things that can be measured and tell you which of them are governed by a published number and which are our own judgement.
Why separate "official" from "ours"?
Because the difference is the whole value. The Passport Office publishes exact pixel and file-size limits, so failing those is a fact. It also says the background must be "plain light-coloured" without publishing any threshold for plainness — so any tool reporting a pass or fail there, including this one, has invented a cutoff. Most checkers present both kinds of result identically, which quietly turns an opinion into an authority.
Why can it not check my head size?
Head height is measured from the bottom of the chin to the crown of the skull — not the top of the hair, which is what a face-detection box would find. The gap between those two is often several millimetres, which is most of the five-millimetre window the rules allow. Rather than guess, the passport tool has you place two marks and computes the crop from them.
Does my photo get uploaded to check it?
No. Everything on this page is measured by code running in your browser, and the page is served with a security policy that blocks the browser from making network requests to anywhere else at all. You can watch the network tab while you run a check.
It says my background is not plain, but it is a plain wall.
Two things commonly cause that. A shadow cast on the wall by your own head reads as variation, which is why the advice is to stand a metre or more away from it. So does a wall with visible texture — woodchip, render or brick — photographed with a strong side light. Both are real problems for a human checker too, so the reading is usually right even when the wall is genuinely one colour.
What if everything passes?
Then nothing measurable is wrong, which is not the same as acceptance. Expression, glasses glare, head coverings, red eye and whether the photo is a scan of a print are all outside what any measurement can see, and so is the head height until you mark it. Read the official guidance before you submit.