You need to be enrolled at least half-time to qualify for an education credit, which I surmise you are concerned about. It wouldn't matter if you were just taking online courses.
Per IRS regulations ""You have to be enrolled at least half time in a program leading toward a degree, certificate or other recognized educational credential for at least one academic period during the tax year."
You can read more about that here:
https://www.irs.gov/credits-deductions/individuals/education-credits-questions-and-answers
As a practical matter, it will often by marked on your form 1098-T if the educational institution considered you to be enrolled at least half-time.