By far, one of the most important questions you should ask of any university is this: Is the school accredited? Most campus colleges that you come across are accredited by multiple organizations, but not all online schools have that same accreditation. In fact, at one time, most online universities were not accredited, and it was extremely hard to tell the legitimate programs from the diploma mills and scams.

Accreditation is a process in which a third party (typically a national organization) reviews an educational program to see if it actually prepares students for a job in their field. If a school is accredited, your diploma is worth more than just the paper on which it’s printed, and employers will recognize it the same as they would a diploma from a regular school. This is opposed to a diploma mill, which is the name for a so-called online university that essentially gives a degree to anyone who has the money for tuition. There are few requirements to get your degree from a diploma mill, and even if you do have classes, they may not be taught by anyone who has experience in your field. You aren’t prepared for a career by purchasing your diploma, so most employers won’t hire someone who hasn’t completed an accredited program.

You can also be scammed if the university you “attend” isn’t accredited. Although rarer than it was in the past, there are still cases of scammers taking tuition money and disappearing. Accreditation ensures that the program really does exist and that your money will go toward a quality education

That’s not to say all unaccredited programs are bad. Some programs are still going through the review process to be accredited. Others choose not to be accredited for one reason or another. Without accreditation, you could still learn valuable skills, but you need that certification that the program is valid to be considered for most jobs.

Accreditation, in addition, is vital for fields where you have to register or get a license. For example, in most medical-related fields, you need a license from a national organization in order to get a job, and along with an exam, most require that you’ve completed an accredited program to get your degree.

So, how do you ensure that the online universities that you’re considering are accredited? Start by searching with the U.S. Department of Education’s Office of Postsecondary Education. This department does not itself accredit colleges, either online or offline, but it does maintain a database of all colleges that have been accredited by legitimate national services.

You should also check with licensing or registration boards if you need to have this kind of certification in your career field. Most will require a degree from a program accredited by a specific organization, so you can contact this organization directly to find out if the online university in question is accredited. Never take their word for it, and beware of any program that announces that they’re “seeking accreditation.” Remember, anyone, regardless of quality, can seek accreditation, so that’s not a good measure of legitimacy. Stick instead to programs that have been accredited already and continue to provide quality programs to their students when choosing a college.