Corrections, questions and partnership mail: hello@passportphoto.buyerguidehq.com
The most useful message contains the document you are applying for, the official page you are reading, and the number that does not match what this site says. Specification errors are treated as the most serious kind of bug on this site, because a wrong millimetre figure can cost someone a second appointment, and reports with an official link attached are usually resolved within days.
A few things this site cannot help with. We cannot review your actual photo and tell you it will be accepted — only the authority you are filing with can do that, and the checker is deliberately honest about being a first pass rather than an approval. We cannot advise on immigration status, appointment availability or processing times. And we cannot confirm a photo for a document whose official page we have not been able to read; those cases are marked on the page itself, with a link to the authority.
Feature requests are read and often acted on: support for another country's document, a new measurement in the checker, or a clearer explanation of a rule that took two readings to understand. If several people ask for the same thing it moves to the top of the list.