How does ShortPixel Image Optimizer work on multisite?

A WordPress multisite, as you may know, works slightly different than a regular WordPress site. If you'd like to use ShortPixel Image Optimizer on a multisite, you have two options:

1. if not all individual sites should have the plugin installed, install but do not activate the plugin from the Network Admin screen. Then, activate it manually on each individual site of the multisite.
2. if all individual sites should have the plugin installed, install and activate the plugin from the Network Admin screen.

Once you have done that, the Settings menu appears (Settings > ShortPixel) and you can add the API key for each individual site. 

As an alternative, you can edit the wp-config.php file and add the following line,

 define('SHORTPIXEL_API_KEY', '<<your api key here>>');

where <<your api key here>> is the API key received upon sign up. If configured this way, the API key will be used for all the individual sites of the multisite but will only be visible on the settings page of the main site, being hidden for the rest of the sites.