Hygger has a Guest role for external users. If you want to invite colleagues or management, stakeholders, so they can see board and comment tasks on it, but not be able to edit - invite them as Guests.

Guests are not paid users and you can invite several users at once. You invite them as you invite Regular Employees or Admin. Click on the “Invite members” button on the header and choose one of way to do it - by invitation on email or with the invitation link. 

Once they confirmed their invitation, they will see only the boards you assigned them to. Guests will be able to see and open tasks, add attachments, subscribe to a task and leave a comment, that’s all. Other options, such as delete, edit or score won’t be available for them. 

Anytime you can upgrade them to Regular Employees on the Company Settings=>Members.