ManyChat uses a two-steps websites authorisation:
1 step: adding website domain into the list (aka 'whitelisting')
2 step: placing ManyChat SDK (js script) into <head> section of your website pages
Step 1 details
Whitelist defines the websites where ManyChat widgets can be displayed. Some widgets (highlighted below) require ManyChat and Facebook whitelisting because for displaying them we utilise Facebook SDK. When you add your websites into the "Authorize website" section, we save them into ManyChat whitelist and check if they can be added into the FB whitelist - this check happens instantly and the result is indicated in UI.
In case of Facebook didn't authorise your website, we mark it with the ⚠️ sign in Settings -> Growth Tools and in particular growth tools Setup section.
Some widgets (SMS Modal) require only ManyChat whitelisting as we render them solely relying on our SDK.
Step 2 details
JS script added to your website connects it with your ManyChat account and renders activated widgets.
These two steps together ensure that your widgets will be displayed only on your websites.