Pass your CDL exam on the first try.

What is a CDL, exactly?

A Commercial Driver's License (CDL) is the federal-level credential required to operate large or specialized commercial motor vehicles in the United States. The Federal Motor Carrier Safety Administration (FMCSA) sets the minimum knowledge and skills standards through 49 CFR Part 383, and every state issues licenses that meet or exceed those standards. That means the basic knowledge tested on a CDL exam is consistent across the country, but the exact wording, scoring, fee structure, and scheduling are handled state by state.

There are three classes of CDL. Class A covers any combination of vehicles with a gross combination weight rating (GCWR) of 26,001 pounds or more, provided the towed unit is over 10,000 pounds — think tractor-trailers and most flatbeds. Class B covers single vehicles over 26,001 pounds and the smaller trailers they may tow — straight trucks, dump trucks, and many buses. Class C covers vehicles that don't meet A or B but are designed to carry 16+ passengers (including the driver) or any quantity of hazardous materials that requires placards.

On top of the class, drivers can add endorsements for specific cargo or vehicle types. The most common are H (Hazmat), N (Tank), T (Double/Triple Trailers), P (Passenger), and S (School Bus). Each endorsement adds its own knowledge test, and Hazmat additionally requires a TSA security threat assessment. Air-brake-equipped vehicles also require passing the Air Brakes knowledge test, or you'll have an L-restriction printed on your license.

CDL Prep Hub mirrors that structure so you can study the way you'll be tested: choose your state, then drill the endorsements you need. The General Knowledge test is the foundation — every CDL applicant takes it — and our study notes follow the same chapter order as the official FMCSA-aligned state handbooks.