For tech things I would say that just reading the documentation (or source if there isn't any useful documentation) is preferable to any online courses.
I'm a big fan of the "teach yourself by reading the docs" thing and I've done a lot of that in my career. But since I started doing a lot of these online courses, I've found that they can be very beneficial. Having a little bit of structure around the learning process, having "classmates" to discuss with, etc. have helped me as I've been (for example) learning R. Now, could I learn R by just reading books, tutorials, and experimenting on my own? Sure, of course. But the courses are pretty cheap, add a little bit of rigor to the process, and come with a minor credential from a well known / highly regarded university (Johns Hopkins, specifically). All in all, I've found that this approach works really well.
Just to share an example of one regard in which the online classes have had value above and beyond me simply doing it entirely on my own... The "R ecosystem" has a LOT of stuff in it. If I just started playing around with R, I'd have little clue which libraries and other tools to try out. But the courses I've done so far have guided me towards learning things like ggplot, dplyr, knitr, etc. Knitr in particular turns out to be really cool, and I'm glad I discovered it... but I don't think it's something I would have gone looking for on my own. Maybe I would still have found it eventually anyway, but as it stands, I feel like the course approach guided me in some useful directions early on.
I'm a big fan of the "teach yourself by reading the docs" thing and I've done a lot of that in my career. But since I started doing a lot of these online courses, I've found that they can be very beneficial. Having a little bit of structure around the learning process, having "classmates" to discuss with, etc. have helped me as I've been (for example) learning R. Now, could I learn R by just reading books, tutorials, and experimenting on my own? Sure, of course. But the courses are pretty cheap, add a little bit of rigor to the process, and come with a minor credential from a well known / highly regarded university (Johns Hopkins, specifically). All in all, I've found that this approach works really well.
Just to share an example of one regard in which the online classes have had value above and beyond me simply doing it entirely on my own... The "R ecosystem" has a LOT of stuff in it. If I just started playing around with R, I'd have little clue which libraries and other tools to try out. But the courses I've done so far have guided me towards learning things like ggplot, dplyr, knitr, etc. Knitr in particular turns out to be really cool, and I'm glad I discovered it... but I don't think it's something I would have gone looking for on my own. Maybe I would still have found it eventually anyway, but as it stands, I feel like the course approach guided me in some useful directions early on.
YMMV, of course.