Masquerading is making an API call on behalf of another user. It will behave as if the target user had made the API call with his own access token (even if he doesn't have one), including permission checks, enrollments, etc. In order to masquerade via the API, the calling user must have the "Become other users" permission. If the target user is also an admin, the calling user must additionally have every permission that the target user has. For auditing purposes, all calls log both the calling user and the target user.

To masquerade, add an as_user_id parameter to any request. It can be either a Canvas user ID, or an SIS user ID (as described in SIS IDs):

curl 'https://<canvas>/api/v1/users/self/activity_stream?as_user_id=sis_user_id:brian' \
     -H "Authorization: Bearer <token>"

Masquerading could be useful in a number of use cases: