Best Practice: separate server w/ hardcoded server_name
Best practice with nginx is to use a separate server for a redirect like this (not shared with the server of your main configuration), to hardcode everything, and not use regular expressions at all.
It may also be necessary to hardcode the domains if you're using HTTPS, because you have to know upfront which certificates you'll be providing.
server {
server_name www.example.com;
return 301 $scheme://example.com$request_uri;
}
server {
server_name www.example.org;
return 301 $scheme://example.org$request_uri;
}
server {
server_name example.com example.org;
# real configuration goes here
}
Using Regular Expressions within server_name
If you have a number of sites, and don't care for the most ultimate performance, but want every single one of them to have the same policy in regards to the www. prefix, then you can use regular expressions. The best practice of using a separate server would still stand.
Note that this solution gets tricky if you use https, as you must then have a single certificate to cover all of your domain names if you want this to work properly.
non-www to www w/ regex in a dedicated single server for all sites:
server {
server_name ~^(?!www\.)(?<domain>.+)$;
return 301 $scheme://www.$domain$request_uri;
}
www to non-www w/ regex in a dedicated single server for all sites:
server {
server_name ~^www\.(?<domain>.+)$;
return 301 $scheme://$domain$request_uri;
}
www to non-www w/ regex in a dedicated server for some sites only:
It may be necessary to restrict the regex to cover only a couple of domains, then you can use something like this to only match www.example.org, www.example.com and www.subdomain.example.net:
server {
server_name ~^www\.(?<domain>(?:example\.org|example\.com|subdomain\.example\.net))$;
return 301 $scheme://$domain$request_uri;
}
Testing Regular Expressions w/ nginx
You can test that the regex works as expected with pcretest on your system, which is the exact same pcre library that your nginx will be using for regular expressions:
% pcretest
PCRE version 8.35 2014-04-04
re> #^www\.(?<domain>(?:example\.org|example\.com|subdomain\.example\.net))$#
data> test
No match
data> www.example.org
0: www.example.org
1: example.org
data> www.test.example.org
No match
data> www.example.com
0: www.example.com
1: example.com
data> www.subdomain.example.net
0: www.subdomain.example.net
1: subdomain.example.net
data> subdomain.example.net
No match
data> www.subdomain.example.net.
No match
data>
Note that you don't have to worry about trailing dots or case, as nginx already takes care of it, as per nginx server name regex when "Host" header has a trailing dot.
Sprinkle if within existing server / HTTPS:
This final solution is generally not considered to be the best practice, however, it still works and does the job.
In fact, if you're using HTTPS, then this final solution may end up easier to maintain, as you wouldn't have to copy-paste a whole bunch of ssl directives between the different server definitions, and could instead place the snippets only into the needed servers, making it easier to debug and maintain your sites.
non-www to www:
if ($host ~ ^(?!www\.)(?<domain>.+)$) {
return 301 $scheme://www.$domain$request_uri;
}
www to non-www:
if ($host ~ ^www\.(?<domain>.+)$) {
return 301 $scheme://$domain$request_uri;
}
hardcoding a single preferred domain
If you want a little bit more performance, as well as consistency between multiple domains a single server may use, it might still make sense to explicitly hardcode a single preferred domain:
if ($host != "example.com") {
return 301 $scheme://example.com$request_uri;
}
References:
Dashboard > Settings > General Settingsand make sure that there is nowwwin the WordPress Address / Site Address URLs. No matter how you configure your nginx, if you have a www in these URLs it would get redirected to the one with www in it. – Cottar