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cpp-httplib/docs-src/pages/en/cookbook/t03-ssl-server.md
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---
title: "T03. Start an SSL/TLS Server"
order: 44
status: "draft"
---
To stand up an HTTPS server, use `httplib::SSLServer` instead of `httplib::Server`. Pass a certificate and private key to the constructor, and you get back something that works exactly like `Server`.
## Basic usage
```cpp
#define CPPHTTPLIB_OPENSSL_SUPPORT
#include <httplib.h>
int main() {
httplib::SSLServer svr("cert.pem", "key.pem");
svr.Get("/", [](const auto &req, auto &res) {
res.set_content("hello over TLS", "text/plain");
});
svr.listen("0.0.0.0", 443);
}
```
Pass the server certificate (PEM format) and private key file paths to the constructor. That's all you need for a TLS-enabled server. Registering handlers and calling `listen()` work the same as with `Server`.
## Password-protected private keys
The fifth argument is the private key password.
```cpp
httplib::SSLServer svr("cert.pem", "key.pem",
nullptr, nullptr, "password");
```
The third and fourth arguments are for client certificate verification (mTLS, see T04). For now, pass `nullptr`.
## Load PEM data from memory
When you want to load certs from memory instead of files, use the `PemMemory` struct.
```cpp
httplib::SSLServer::PemMemory pem{};
pem.cert_pem = cert_data.data();
pem.cert_pem_len = cert_data.size();
pem.key_pem = key_data.data();
pem.key_pem_len = key_data.size();
httplib::SSLServer svr(pem);
```
Handy when you pull certificates from environment variables or a secrets manager.
## Rotate certificates
Before a certificate expires, you may want to swap it out without restarting the server. That's what `update_certs_pem()` is for.
```cpp
svr.update_certs_pem(new_cert_pem, new_key_pem);
```
Existing connections keep using the old cert; new connections use the new one.
## Generating a test certificate
For a throwaway self-signed cert, use the `openssl` CLI.
```sh
openssl req -x509 -newkey rsa:2048 -days 365 -nodes \
-keyout key.pem -out cert.pem -subj "/CN=localhost"
```
In production, use certificates from Let's Encrypt or your internal CA.
> **Warning:** Binding an HTTPS server to port 443 requires root. For a safe way to do that, see the privilege-drop pattern in S18. Control Startup Order with `listen_after_bind`.
> For mutual TLS (client certificates), see T04. Configure mTLS.