ID and passport photo

Whatever the form asks for — it always says. Passports follow the international 35 × 45 mm standard, which the EU and the UK use as well; a US visa photo is 51 × 51 mm, that is 2 × 2 inches; and 3 × 4 cm and 4 × 5 cm are the everyday sizes across Latin America. Each button shows both its millimetres and its pixels, so you can check them against your form before you create anything.

No. The colour you pick fills the margin — the border around the photo — and any transparent areas of the image you upload. Nothing else. If there is a wall behind you, the wall stays. For a genuinely white background, the thing that works is taking the photo against a plain, well-lit wall.

Enough that the area you frame holds at least the pixels of the size you picked — 413 × 531 for a passport, for instance. Any phone from the last decade clears that easily as long as you do not crop in too tightly. If you fall short, the tool tells you with the exact numbers and still creates the photo, but it is scaled up and will look soft in print.

Both. The file comes out at the pixel count that matches the size at 300 dpi, the resolution print shops and online applications both accept. JPG is what any photo lab reads; PNG is there for the forms that insist on it.

No. The crop, the size and the margin are all worked out inside your browser. You can confirm it with the Network tab of your developer tools open, or by disconnecting the internet once the page has loaded: the tool keeps working exactly the same.