We could collect the major facts about groups vs circles here and contribute them as part of the circles app description, what you think?
The clearer things are, the more admins/users might consider to use it and the greater the interest to extend support from other apps.
This is how I understand it:
- Groups are a Nextcloud core feature. As such support from other apps is mostly present right from the beginning.
- Groups are valid and accessible throughout the whole Nextcloud instance, which inherits that they can be used to grant global permissions of any kind and as such they can be used by admins to apply a general organisation structure.
- Circles on the other hand are a grouping layer only on user level. Thus every user can create them, but they are only visible/valid for the particular user. This inherits that they cannot be used for instance-wide/global permissions of any kind.
- Users may use their own circles for sharing, e.g. if the instances-wide groups don’t fit their needs, e.g. they want to exclude particular users of one group and/or include particular users of another group for their shares.
- Since circles are a separate app and no core feature, it is expected that they are not supported by all other apps.
Although for usability it would be great if every app that uses the group API, did add the circles of the current user just into the same list. This should be not too hard to implement and we might want to open feature requests for that, where missing.
Another option would be to just add circles to the groups API, so that every request to show groups for selection, would add the particular users circles to the same list, as long as it is about user-level and not admin/global-level permissions of any kind. This would render all coding for apps obsolete to add circles support, but it would add code to core that is not require for all instances that don’t use the circles app.
Not sure which is best, but both options are worth to consider.