Craft REST APIs in C++ as Easily as You Do in Flask!

Interactive CrowCpp “Getting Started” Tutorial with Hands-On Example

This step-by-step tutorial will guide you through building and running your first web application using the Crow C++ microframework. Crow is inspired by Python’s Flask, making REST APIs and simple web servers with C++ much easier and more accessible.

1. Installation Requirements

Before starting, ensure you have these installed on your system:

• C++11+ compiler (GCC, Clang, MSVC)
• Boost library with ASIO headers
• (Optional but recommended): CMake

2. Setting Up Crow

Crow has a single-header version, which you can use by downloading crow_all.h.

Download the Crow header:

• Download crow_all.h from Crow’s GitHub releases or source files.
• Place it in your project folder1.

3. Write Your First Application

Create a file named main.cpp in your project directory and add the following code:

#include "crow_all.h"

int main()
{
    crow::SimpleApp app;

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

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

#include "crow_all.h"

int main()
{
    crow::SimpleApp app;

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

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

• The route / returns “Hello World!” when accessed from your browser or via CURL21.

4. Compile Your Application

On Linux/Mac (with Boost installed):

Run in terminal:

g++ main.cpp -o main -std=c++11 -pthread -lboost_system

g++ main.cpp -o main -std=c++11 -pthread -lboost_system

On Windows:

• Use a compatible compiler (e.g., MSVC or MinGW), ensuring Boost is correctly referenced. Don’t use windows personally but drop in comment if you are interested me to explain more.

5. Run Your Web Server

In your terminal:

./main

./main

• The server will run on http://127.0.0.1:18080/.

6. Interact with Your Server

• Open a web browser and visit http://127.0.0.1:18080/
• You should see Hello World! displayed.

Or, via terminal:

curl http://127.0.0.1:18080/

curl http://127.0.0.1:18080/

7. Make It Interactive: Try Editing Your Route

Now, let’s get hands-on! Change the route or add more:

Example: Add a /hello/<name> route to greet users by name.

CROW_ROUTE(app, "/hello/<string>")
([](std::string name){
    return "Hello, " + name + "!";
});

CROW_ROUTE(app, "/hello/<string>")
([](std::string name){
    return "Hello, " + name + "!";
});

Recompile and rerun your app.

• Navigate to http://127.0.0.1:18080/hello/Alex — it should display Hello, Alex!.

8. We will explore more on following topic:

• Add routes for POST, PUT, DELETE.
• Try returning JSON with crow::json::wvalue.
• Explore middleware for authentication and logging.
• Deploy on another port: app.port(8080).run();
• Add HTTPS support with OpenSSL (see Crow docs).
• Crow template engine (Mustache)

💡 Tips

• Crow uses modern C++ idioms, so prior experience with REST in C++ is not necessary.
• If you have trouble compiling, check your Boost installation and that you’re linking with -lboost_system.

You’ve now built and run your first Crow web application! Experiment further by customizing the routes and integrating business logic. This is only the beginning—Crow offers a rich set of features for building serious web servers and APIs in C++.

For more advanced examples and in-depth guides, visit the official Crow documentation or their GitHub page.

Checkout how to use template engine here.