crowsite/libs/crow/docs/guides/ssl.md

Crow supports HTTPS though SSL or TLS.

!!! note

When mentioning SSL in this documentation, it is often a reference to openSSL, which includes TLS.<br><br>

To enable SSL, first your application needs to define either a .crt and .key files, or a .pem file. Once you have your files, you can add them to your app like this:
#!cpp app.ssl_file("/path/to/cert.crt", "/path/to/keyfile.key") or #!cpp app.ssl_file("/path/to/pem_file.pem"). Please note that this method can be part of the app method chain, which means it can be followed by .run() or any other method.

You also need to define CROW_ENABLE_SSL in your compiler definitions (g++ main.cpp -DCROW_ENABLE_SSL for example) or set(CROW_FEATURES ssl) in CMakeLists.txt.

You can also set your own SSL context (by using asio::ssl::context ctx) and then applying it via the #!cpp app.ssl(ctx) method.

!!! warning

If you plan on using a proxy like Nginx or Apache2, **DO NOT** use SSL in crow, instead define it in your proxy and keep the connection between the proxy and Crow non-SSL.