cpp-httplib/docs-src/pages/en/tour/05-tls-setup.md

title, order

title	order
TLS Setup	5

So far we've been using plain HTTP, but in the real world, HTTPS is the norm. To use HTTPS with cpp-httplib, you need a TLS library.

In this tour, we'll use OpenSSL. It's the most widely used option, and you'll find plenty of resources online.

Installing OpenSSL

Install it for your OS.

OS	How to install
macOS	Homebrew (brew install openssl)
Ubuntu / Debian	sudo apt install libssl-dev
Windows	vcpkg (vcpkg install openssl)

Compile Options

To enable TLS, define the CPPHTTPLIB_OPENSSL_SUPPORT macro when compiling. You'll need a few extra options compared to the previous chapters.

# macOS (Homebrew)
clang++ -std=c++17 -DCPPHTTPLIB_OPENSSL_SUPPORT \
    -I$(brew --prefix openssl)/include \
    -L$(brew --prefix openssl)/lib \
    -lssl -lcrypto \
    -framework CoreFoundation -framework Security \
    -o server server.cpp

# Linux
clang++ -std=c++17 -pthread -DCPPHTTPLIB_OPENSSL_SUPPORT \
    -lssl -lcrypto \
    -o server server.cpp

# Windows (Developer Command Prompt)
cl /EHsc /std:c++17 /DCPPHTTPLIB_OPENSSL_SUPPORT server.cpp libssl.lib libcrypto.lib

Let's look at what each option does.

• -DCPPHTTPLIB_OPENSSL_SUPPORT — Defines the macro that enables TLS support
• -lssl -lcrypto — Links the OpenSSL libraries
• -I / -L (macOS only) — Points to the Homebrew OpenSSL paths
• -framework CoreFoundation -framework Security (macOS only) — Needed to automatically load system certificates from the Keychain

Verifying the Setup

Let's make sure everything works. Here's a simple program that passes an HTTPS URL to httplib::Client.

#define CPPHTTPLIB_OPENSSL_SUPPORT
#include "httplib.h"
#include <iostream>

int main() {
    httplib::Client cli("https://www.google.com");

    auto res = cli.Get("/");
    if (res) {
        std::cout << "Status: " << res->status << std::endl;
    } else {
        std::cout << "Error: " << httplib::to_string(res.error()) << std::endl;
    }
}

Compile and run it. If you see Status: 200, your setup is complete.

Other TLS Backends

cpp-httplib also supports Mbed TLS and wolfSSL in addition to OpenSSL. You can switch between them just by changing the macro definition and linked libraries.

Backend	Macro	Libraries to link
OpenSSL	CPPHTTPLIB_OPENSSL_SUPPORT	libssl, libcrypto
Mbed TLS	CPPHTTPLIB_MBEDTLS_SUPPORT	libmbedtls, libmbedx509, libmbedcrypto
wolfSSL	CPPHTTPLIB_WOLFSSL_SUPPORT	libwolfssl

Mbed TLS 2.x, 3.x, and 4.x are all supported and auto-detected. Note that Mbed TLS 4.x renames libmbedcrypto to libtfpsacrypto, so link against that instead.

This tour assumes OpenSSL, but the API is the same regardless of which backend you choose.

Next Step

You're all set with TLS. Next, let's send a request to an HTTPS site.

Next: HTTPS Client