Most drivers assemble their glovebox contents by accident and discover the gaps during a traffic stop or after a collision, which are the two worst moments to find out something is missing or expired.
The Three You Will Actually Be Asked For
Your driver license, the vehicle registration, and proof of insurance. An officer conducting a routine stop will generally ask for all three, and being unable to produce them can turn a warning into a citation even when nothing else is wrong.
Your license belongs on your person rather than in the vehicle, since it is identification rather than a vehicle document.
Digital Versions
Many states now accept electronic proof of insurance, and a growing number accept digital licenses. Acceptance is not universal, and a phone with a dead battery is no proof of anything.
Keep paper copies regardless. The cost is nothing and the failure mode of the digital version is entirely predictable.
What Belongs in the Glovebox
Registration and insurance card. A copy of any inspection or emissions certificate your state requires. The owner's manual, which is more useful than people assume when a warning light appears.
Add a written note with emergency contacts, any medical conditions or allergies responders should know about, and your insurer's claims number. If you are unconscious after a collision, that note does work nothing on your phone can do behind a lock screen.
A basic collision kit is worth including. A pen, a card for recording the other driver's details, and a reminder to photograph the scene, both vehicles, and the surrounding road.
What Should Not Live in Your Car
Your vehicle title. It is the ownership document, and leaving it in the glovebox of a stolen car is an unforced error. Keep it at home.
Spare keys, garage remotes when the vehicle is parked outside, and documents carrying your full personal details beyond what is required.
Keep Them Current
Expired insurance cards are extremely common, because the replacement arrives by email and never makes it to the car. Set a reminder when the policy renews, and check the registration expiry at the same time.
Document requirements and digital acceptance rules vary. Check what your state requires, and see vehicle registration rules if you have recently bought or moved a vehicle.