Unable to add "location /" to additional nginx directives for domain in Plesk: nginx: [emerg] duplicate location "/"

Symptoms

nginx is enabled as the reverse proxy in Plesk.

If try adding the below directives in Plesk in Domains > example.com > Apache & nginx Settings > Additional nginx directives:

CONFIG_TEXT: location / {
..........
}

The following error occurs:

PLESK_ERROR: Invalid nginx configuration: nginx: [emerg] duplicate location "/" in /data/www/system/example.com/conf/vhost_nginx.conf:1 nginx: configuration file /etc/nginx/nginx.conf test failed

Cause

Location / is already defined in the main domain configuration file /var/www/vhosts/system/example.com/conf/nginx.conf.

Resolution

If additional directives should be added to the location /, it can be done using the custom virtual hosts configuration templates. See the below documentation article for more details:

Changing Virtual Hosts Settings Using Configuration Templates

Warning: The changes in the virtual hosts configuration templates are applied to all domains on the server.

Alternatively, disable proxy mode for the domain example.com so only nginx is used for serving the domain. In this case, it is possible to define location / in Plesk in Domains > example.com > Apache & nginx Settings > Additional nginx directives.