What have been the most helpful online tools to self-improve as a developer/software engineer (from bootcamps to university degrees)?

I'm a little late on this topic, so I apologize. However, I find this a very important topic as a student and a web developer.

I use all types of resources and online tools to help me improve. Some include freeCodeCamp.org to help learn by doing. Others are websites that contain articles like hashnode or medium.com. Which is tailored to what I like to read and need assistance with. Medium is especially useful because you can save several articles and make lists and even follow the authors.

I also have joined some web development groups on Facebook which is very helpful and when you have someone to talk to you and help you out with something you don't know, it is extremely helpful. Some examples are: Women+ in Web Development, HTML, CSS, & JavaScript, and UI/UX Designers & Developers.

These are just some of the resources I find helpful to me. Let me know what you find helpful.