It is a perfect tool for beginners and experts too. The beginner can easily try functionality to better understanding and validate ideas. The expert could understand code more deeply. How compilers see theirs code and what is possible for a compiler to optimize. Sometimes is hard to decide why some block of code is faster than another. This tool also can help fast solve differences between compilers.

Online Compilers of C++ code are the best solution for a fast try or test behavior. I personally learn new C++ features by reference and try them online. There are plenty of tools therefore I sort it from my personal point of view to this list with pros and cons.

source: https://www.techgeekbuzz.com/best-online-cpp-compiler/