@AgneseNg This is a question best asked to your school's IT help desk. This community is fellow Canvas users around the globe to help with how to best use Canvas. The "lockdown browser" is also a tool that is added to Canvas and it not part of Canvas itself. I am guessing you are referring to Respondous but there are other ones your institution could be using as well (for example my university uses Proctorio).
Hope this helps!
Nick
