Since Nginx 1.13, support has been added for TLSv1.3, the latest version of the TLS protocol. Depending on when you read this post, chances are you're running an older version of Nginx at the moment, which doesn't yet support TLS 1.3. In that case, consider running Nginx in a container for the latest version, or compiling Nginx from source.
Enable TLSv1.3 in Nginx
I'm going to assume you already have a working TLS configuration. It'll include configs like these;
... ssl_protocols TLSv1 TLSv1.1 TLSv1.2; ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256; ssl_prefer_server_ciphers on; ssl_ecdh_curve secp384r1; ...
And quite a few more parameters.
To enable TLS 1.3, add
TLSv1.3 to the
ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
And reload your Nginx configuration.
Test if your Nginx version supports TLS 1.3
Add the config as shown above, and try to run Nginx in debug mode.
$ nginx -t nginx: [emerg] invalid value "TLSv1.3" in /etc/nginx/conf.d/ma.ttias.be.conf:34 nginx: configuration file /etc/nginx/nginx.conf test failed
If you see the message above, your Nginx version doesn't support TLS 1.3. A working config will tell you this;
$ nginx -t nginx: the configuration file /etc/nginx/nginx.conf syntax is ok nginx: configuration file /etc/nginx/nginx.conf test is successful
If you don't see any errors, your Nginx version supports TLS 1.3.
Now that you've told Nginx to use TLS 1.3, it will use TLS 1.3 where available, however ... there aren't many libraries out there that offer TLS 1.3.
For instance, OpenSSL is still debating the TLS 1.3 implementation, which seems reasonable because to the best of my knowledge, the TLS 1.3 spec isn't final yet. There's TLS 1.3 support included in the very latest OpenSSL version though, but there doesn't appear to be a sane person online that actually uses it.
TLSv1.3 draft-19 support is in master if you "config" with "enable-tls1_3". Note that draft-19 is not compatible with draft-18 which is still be used by some other libraries. Our draft-18 version is in the tls1.3-draft-18 branch.
TLS 1.3 support in OpenSSL
In short; yes, you can enable TLS 1.3 in Nginx, but I haven't found an OS & library that will allow me to actually use TLS 1.3.