OpenID Connect implementations use iframes for logout, because that's what the spec says. Iframes are a third party context. The big Identity companies (Ping, O

OpenID Connect implementations use iframes for logout, because that's what the spec says. Iframes are a third party context. The big Identity companies (Ping, Oracle, Microsoft) wrote the OpenID Connect spec. Google may be the odd man out (they are notorious for implementing logout poorly in general) but the biggest enterprise authentication services use iframes for logout. There is a compromise here which works for logout which was commonly implemented for a few years - supporting third party cookie clear but not set. But Apple ended this norm.