Is Facebook Audience Network Mobile Web not available?

Question

What does it mean by Closed Beta?

https://www.facebook.com/audiencenetwork/overview

Is this service available to a restricted group? How can one participate in this closed beta project?

Answer 1

The service is not available to the public. As of April 2017 the page for web integration still displays a notice stating that mobile web integration is available only to certain publishers.

This article gives a good rundown on why they're moving slowly into the web-space, and implies that to become a part of the closed beta you'll need to be a big fish i.e. Facebook will contact you if you're to be included.