The QuantLib C++ library

Open source analytics and market risk library from OpenGamma

A markup-based typesetting system that is powerful and easy to learn.

Light-weight, simple and fast XML parser for C++ with XPath support

OCILIB (C and C++ Drivers for Oracle) - Open source C and C++ library for accessing Oracle databases

A C++ static library offering a clean and simple interface to the 7-zip shared libraries.

Sol3 (sol2 v3.0) - a C++ <-> Lua API wrapper with advanced features and top notch performance - is here, and it's great! Documentation:

TinyXML2 is a simple, small, efficient, C++ XML parser that can be easily integrated into other programs.

A modern, C++-native, test framework for unit-tests, TDD and BDD - using C++14, C++17 and later (C++11 support is in v2.x branch, and C++03 on the Catch1.x branch)

A modern, C++11-native, single-file header-only, tiny framework for unit-tests, TDD and BDD (includes C++98 variant)

Crow is very fast and easy to use C++ micro web framework (inspired by Python Flask)

mstch is a complete implementation of {{mustache}} templates using modern C++

A fast JSON parser/generator for C++ with both SAX/DOM style API

JSON for Modern C++

📊 Cross-platform user-friendly xlsx library for C++11+

Cryptography Toolkit

A modern formatting library

SQLCipher is a standalone fork of SQLite that adds 256 bit AES encryption of database files and other security features.

Fast C++ logging library.