Single sign-on across subdomains, explained

When you have more than one product, asking users to create a separate login for each one is a quick way to lose them. Centralized authentication fixes that.

LastAccounts acts as the single sign-on provider for every Lastborn subdomain. Sign in once and your session follows you across the entire ecosystem.

In this post we walk through the design at a high level and the security properties that make a shared session safe.