The WebEngine preview URL is locked from public consumption. As such it will only render if:
The user is logged in and has access to that instance.
A valid password has been provided. This password is set by via the Settings under
category: security and
key: preview_lock_password is set, a user may enter the password to start a verified session.
Once a user is verified by (via password or their user login session), a unique device imprint cookie ZVerified is created and is used to quickly bypass the preview lock for every network request.
Preview Lock Protection exists to protect your un-published changes and to prevent users from using the preview URL in production.
For Instances created before Jan 1, 2021, contact your account manager, as you will need a setting added to your instance. Once the Preview Lock Password text field has been added your preview URL will be password protected.
When the preview URL is being accessed by non-authenticated Zesty users, you may set a Preview Lock Password which prompts an unauthenticated user to enter a password. They may try 5 times before being locked out.