most states allow drivers to go darker (up to 70% tint) on the front side mirrors and even darker on the back side mirrors, but the windshield itself is not allowed to be tinted in all 50 states.

BISMARCK, N.D. (KFGO) – The Secretary of State’s Office has approved a petition for a measure that would change North ...

There is even a marking to tell you where you can add darker tint without breaking windshield tint laws in Texas or other states. The formats for these codes also vary between countries.