MATLAB’s online, free & open-source alternative is Octave Online. It is a web UI for GNU Octave, suitable for studying machine learning, control systems, numerical methods, and more. Every day, thousands of students, educators, and researchers using this open-source and online alternative to MATLAB.
It is a platform-independent tool, so you can run MATLAB codes online, without the need to install anything in your cellphone (mobile), tablet, laptop, etc.! It works on any operating system including Android, iOS, macOS, Windows, Linux, etc.
Moreover, the most popular packages pre-installed (see which ones with “pkg list”). However, if you want a package that is not listed, you can install a custom package in your own account!