The timebox for a Daily Scrum is?

The Scrum Guide states that "The Daily Scrum is a 15-minute time-boxed event for the Development Team to synchronize activities and create a plan for the next 24 hours."1 The Daily Scrum is a quick and simple planning meeting designed to keep everyone in the loop with how other team members are getting on. It ensures that team members are fully aligned with each other and on track to hit the Sprint Goal.

References:

1: The Scrum Guide2, page 11

2: The Scrum Guide