nonstd-lite/byte-lite

variant lite - A C++17-like variant, a type-safe union for C++98, C++11 and later in a single-file header-only library.

optional lite - A C++17-like optional, a nullable object for C++98, C++11 and later in a single-file header-only library

any lite - A C++17-like any, a type-safe container for single values of any type for C++98, C++11 and later in a single-file header-only library

string_view lite - A C++17-like string_view for C++98, C++11 and later in a single-file header-only library

span lite - A C++20-like span for C++98, C++11 and later in a single-file header-only library

Simple Useful Libraries: C++17/20 header-only dynamic bitset

📚 single header utf8 string functions for C and C++

A collection of std-like single-header C++ libraries

Extensions to the C++ standard library. This library implements polyfills to enable library functionality from later versions of C++ to be used in earlier versions. It also implements some nonstandard but useful extras.