The Expect-CT header was designed to allow websites to opt-in to Certificate Transparency enforcement before it was enforced by default. However, as of May 2018, new certificates are expected to support SCTs by default, which makes the Expect-CT header obsolete. Certificates issued before March 2018 were allowed to have a lifetime of 39 months, which all expired halfway 2021.
With the release of the latest Google Chrome browser (105) at the end of August 2022, the Expect-CT header has officially been deprecated and will be removed in version 107. The first deprecation reports have been processed to inform users of the pending removal.
We have removed Expect-CT from our service and highly encourage users who enabled Expect-CT on their websites to remove the header to avoid unnecessary bandwidth usage.