Yesterday I wrote about Chrome Flags; today I'll explain why.
Chrome is currently rolling out sweeping changes to how it handles cookies. I
learned a lot about it this week. To summarize, cookies that don't specify a
SameSite attribute will be treated as SameSite=Lax by Chrome starting with
version 91. Ask for those cookies from a different URL, and Chrome won't share
them. This means that cookies intended for third-party or cross-site sharing
must specify SameSite=None and Secure. You can opt into this behavior today
with the aforementioned flags.
So what? A lot of (sometimes bad) internet behavior relied on open cookie sharing. The web dev community has a lot of work to do to respond to this change.