Comment by ncmncm

Even neglecting Godbolt, Cppreference, and Coliru.

Godbolt is Compiler Explorer, mainly to look at assembly output, but provides editing, benchmarking, and profiling of many languages and compiler versions. I think Godbolt delegates running code to some other site, don't recall who.

Cppreference.com is mainly a C++ and C language and library standards reference library, but provides sample programs and means to run them on various compiler versions.

That uses Coliru, which also provides edit, build, and run.