IEEE 2089.1
IEEE 2089.1 Standard for Online Age Verification was published in May 2024, the result of over two years of deliberation by a working group of industry experts from around the world.
It sets out a best practice process for implementing age verification (including age estimation), beginning by identifying relevant legislation in the jurisdictions where a digital service determines its need to be compliant, then selecting the appropriate methods of age assurance, conducting it, then measuring its level of age assurance, while also ensuring privacy protections, applying data security measures and promoting interoperability.
For the first time, this standard defines a common, multi-dimensional approach to measuring the effectiveness of an age assurance process which can be applied across different methods – including both estimation and verification.

You can access the standard from the IEEE’s website here. ($77, $62 for Members of IEEE, or free by subscription).