The actual CDL Learner's Permit written test is not available online, but most states offer practice materials on their websites. Applicants can book and pay for the tests online in most states, but they must undergo the actual process in person at a designated location.
Designated locations vary between states. Some states have Motor Vehicle Division field offices, but not all of these administer Commercial Driver's Licenses or oversee the tests. Other states use a single test center for all applicants in a geographical area, and some of these run tests on a walk-in basis when applicants provide the correct identification and pay the fee.