[x] There's evidence the domains are currently related (SSL certificates, DNS entries, valid links between sites, legal documents etc.)
[x] If using shared, the new group serves login pages on each of the included domains, and those login pages accept accounts from the others. (For example, we wouldn't use a shared association from google.co.il to google.com, because google.co.il redirects to accounts.google.com for sign in.)
From https://ipv6.he.net/certification/register.php:
Overall Checklist
for shared-credentials.json
shared
, the new group serves login pages on each of the included domains, and those login pages accept accounts from the others. (For example, we wouldn't use ashared
association fromgoogle.co.il
togoogle.com
, becausegoogle.co.il
redirects toaccounts.google.com
for sign in.)