How does Assign To work?

Canvas will assign your assignment to Everyone in your course by default.

You can add more than one Section to the Assign to field as long as the due and availability dates are the same for those Sections.

If you want to set different dates for different sections/groups, click Add below the date pickers, then Assign To the respective Sections and add the dates that apply to those Sections.

This way, you need not create multiple assignments for Sections with different due dates.