A path to the file is constructed by merely adding a URI to the value of the root directive. If a URI has to be modified, the alias directive should be used

Defines a replacement for the specified location. For example, with the following configuration

location /i/ {    alias /data/w3/images/;}

on request of “/i/top.gif”, the file /data/w3/images/top.gif will be sent.

The path value can contain variables, except $document_root and $realpath_root.

If alias is used inside a location defined with a regular expression then such regular expression should contain captures and alias should refer to these captures (0.7.40), for example:

location ~ ^/users/(.+\.(?:gif|jpe?g|png))$ {    alias /data/w3/images/$1;}

When location matches the last part of the directive’s value:

location /images/ {    alias /data/w3/images/;}

it is better to use the root directive instead:

location /images/ {    root /data/w3;}

nginx alias