Skip to content

A Fast and Easy to use microframework for the web.

Build Status Coverage Status Documentation Gitter


Crow is a C++ microframework for running 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)

Still in development


Available here.


Hello World

#include "crow.h"

int main()
    crow::SimpleApp app;

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


JSON Response

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


([](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 paramters"
([](int a, int b){
    return crow::response(500);

Handling JSON Requests

CROW_ROUTE(app, "/add_json")
([](const crow::request& req){
    auto x = crow::json::load(req.body);
    if (!x)
        return 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.

Setting Up / Building

Available here.