Legality often depends on your ability to see clearly and the specific laws of your state or country.
It's recommended to replace the back window as soon as possible. Consider the following scenarios: can i drive with a shattered back window
Check your insurance policy and vehicle warranty to see if they cover back window replacement: Legality often depends on your ability to see
If your car is currently parked in a dangerous spot or you have no other way to get to a repair shop, follow these steps to minimize risk: In most jurisdictions, driving with a shattered window
Legalities aside, the physical dangers of driving without a back window are substantial.
In most jurisdictions, driving with a shattered window is a violation of vehicle safety codes. While laws vary by state and country, the general rule is that a vehicle must be in a safe operating condition.