Speaking in general terms here, because you didn't specify any course specifics. I wouldn't base your trade or part of your career on an online course alone. I

Speaking in general terms here, because you didn't specify any course specifics. I wouldn't base your trade or part of your career on an online course alone. In order for the knowledge to stick you need to apply and practice it (like anything else including traditional classroom learning). However in my experience MOOCs do give you a decent foundation, and likely put you in a position where you know of concepts being discussed in an area where your specific trade is being applied. So my (perhaps unsolicited) advice is to not make the assumption that taking an online course will inundate you with useful knowledge to then go out in the industry and practice it. I think it'll give you a good foundation to either motivate you to gain practical experience or it'll make you aware that this particular trade is not a good fit for you. Edit: To directly answer the original question, yes, I have seriously learned useful things from online courses.