Is an online course certificate worth anything on your resume?
It depends heavily on who issued it. Certificates from university platforms like Coursera and edX, and professional certificates from Google or IBM, are taken seriously by employers. Certificates from open marketplaces like Udemy mostly prove effort, not tested skill.
Employers look at two things in a certificate: who issued it, and was anything actually tested. On Coursera and edX you take courses from real universities, with graded work and exams. A Google or IBM professional certificate via Coursera sits perfectly fine on LinkedIn these days and gets recognized in hiring.
On open marketplaces like Udemy, anyone can publish a course, so the certificate is proof of completion, not of level. That does not make the course worthless: you often learn the actual skill just fine. But put it on your resume as a supporting detail, not a headline.
The golden rule: what ultimately counts with employers is what you can show. A portfolio, a project, a working result says more than any certificate. Pick the course for what it teaches you, and treat the paper as a bonus.