How do you pick a good online course?
Check four things: recent reviews (not just the star rating), the last-updated date, the instructor's background, and whether the syllabus covers your concrete goal. And watch the free preview lessons first; they tell you more than any description.
The supply is overwhelming, but bad picks are avoidable. Start from your goal and work backwards: which skill must you concretely have after the course? Hold the syllabus against that. A course that promises everything usually delivers a little of everything.
Then the quality check. Read reviews smartly: sort by recent (a 2021 course with glowing 2021 reviews may be outdated) and pay attention to what the critical ones say. Check when the course was last updated; for technical topics that is decisive. And look up the instructor: someone who practices the craft teaches you different things than a professional course-maker covering everything.
Finally: taste before you buy. Nearly every platform offers preview lessons, free first chapters (Codecademy, DataCamp), or a trial period. If the pace or style grates in the preview, it will not improve after purchase. And on marketplaces like Udemy: never pay full price; the sale always comes back.