Coauthorship outside my PhD work I am currently a PhD student and I was invited to co-author a review paper on my field. Would it be ok to co-author a paper outside my PhD work without my supervisor as a co-author? My supervisor is supportive of all my work and networking I'm just worried about this kind of move now.
Ask your supervisor.

This will basically come down to your supervisor's wishes. However, it is usually OK. The majority of my papers during PhD were with other coauthors and not my advisor and he was very supportive of this. Personally, I would consider it very poor form for a supervisor to be so possessive of their students' time.

If your supervisor says it's OK, then go for it. If your supervisor objects, then you have to decide what to do. Personally, I would consider finding a better supervisor if my current one won't let me broaden my collaboration network, but it depends on your situation.