Nginx Redirects With Query String Arguments

This is an example of how my Nginx configuration looked to redirect from an old domain to a new one, and also to redirect from the root example.com domain to the canonical www subdomain.

server {
listen 80;

server_name example.com;
server_name my-old-domain.com;
server_name www.my-old-domain.com;

return 301 https://www.example.com$uri;
}

It also redirects the URI value, e.g. from http://example.com/test to http://example.com/test, but I noticed recently though that any the query string would be lost - e.g. http://example.com/?test would redirect to http://www.example.com and the ?test would be dropped. The application that I built references images based on the query string, so I wanted these to be included within the redirect.

This was fixed by making a small change to my return statement.

Before:

return 301 https://www.example.com$uri;

After:

return 301 https://www.example.com$uri$is_args$args;

$is_args is an empty string if there are no arguments, or a ? to signify the start of the query string. $args then adds the arguments ($query_string could also be used with the same result).

Here is an demo of it working on this website:

Resources

Query string

Nginx ngx_http_core_module