Can I see how many members my space has?

Due to Fedi's prioritization of privacy, it is not possible to know how many Fedians have joined your space or to see a list of the members of your space. That said, there is a great opt-in proxy for doing exactly this via the default groups in the Chat Rooms section.

When someone joins your space, they receive view-only access to the groups in the Chat Rooms section of the space, but they are not immediately added to these chat groups – as doing so would reveal their Fedi chat profile without their consent.

This is why new members of a space cannot immediately post messages, even in non-broadcast channels. They must first tap the Join group button in the conversation pane or be directly invited by group admins or moderators (see How do I invite someone to join my chat group?).

Once they either accept a group invitation or tap the Join group button, not only are they be able to post in non-broadcast channels right away – they also become visible to group admins and moderators (who are presumably the same folks running the space) in the chat group member list.

Though chat group members do not necessarily equate to space members – as Fedians can join a space without joining the associated chat groups or leave chat groups but remain in the space – the chat group member list serves as an imperfect but helpful gauge for members of a space.