Crow is a C++ framework for creating HTTP or Websocket web services. It uses routing similar to Python's Flask which makes it easy to use. It is also extremely fast, beating multiple existing C++ frameworks as well as non-C++ frameworks.

• Easy Routing (similar to Flask).
• Type-safe handlers.
• Blazingly fast (see this benchmark and this benchmark).
• Built in JSON support.
• Mustache based templating library (crow::mustache).
• Header only library (single header file available).
• Middleware support for extensions.
• HTTP/1.1 and Websocket support.
• Multi-part request and response support.
• Uses modern C++ (11/14)

• Async support
• HTTP/2 support

Available here.

Warning

If you are using Crow v0.3, then you have to put #define CROW_MAIN at the top of one and only one source file.

#include "crow.h"

int main()
{
    crow::SimpleApp app;

    CROW_ROUTE(app, "/")([](){
        return "Hello world";
    });

    app.port(18080).multithreaded().run();
}

CROW_ROUTE(app, "/json")
([]{
    crow::json::wvalue x({{"message", "Hello, World!"}});
    x["message2"] = "Hello, World.. Again!";
    return x;
});

CROW_ROUTE(app,"/hello/<int>")
([](int count){
    if (count > 100)
        return crow::response(400);
    std::ostringstream os;
    os << count << " bottles of beer!";
    return crow::response(os.str());
});

Handler arguments type check at compile time

// Compile error with message "Handler type is mismatched with URL parameters"
CROW_ROUTE(app,"/another/<int>")
([](int a, int b){
    return crow::response(500);
});

CROW_ROUTE(app, "/add_json")
.methods("POST"_method)
([](const crow::request& req){
    auto x = crow::json::load(req.body);
    if (!x)
        return crow::response(crow::status::BAD_REQUEST); // same as crow::response(400)
    int sum = x["a"].i()+x["b"].i();
    std::ostringstream os;
    os << sum;
    return crow::response{os.str()};
});

More examples can be found here.

Available here.

CrowCpp/Crow is a project based on ipkn/crow. Neither CrowCpp, it's members, or this project have been associated with, or endorsed or supported by ipkn (Jaeseung Ha) in any way. We do use ipkn/crow's source code under the BSD-3 clause license and sometimes refer to the public comments available on the github repository. But we do not in any way claim to be associated with or in contact with ipkn (Jaeseung Ha) regarding CrowCpp or CrowCpp/Crow

Crow has incorporated the following libraries into its source.