Ory is the largest open source community in the world for cloud software application security. We maintain advanced open source security software solving authentication, authorization, access control, application network security, and delegation. Ory implements a variety of industry and best-practice standards including OAuth 2.0 / OAuth 2.1, OpenID Connect, Zero Trust Networking, Google Zanzibar Policy Framework, FIDO2 U2F, WebAuthn, TOTP, and more.

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Q: what's the purpose of setting the kratos cookie domain to something broader than the domain that kratos itself is running on? Don't those cookies only need to go to kratos? Other services never need to read them, correct?

I'm mainly talking about the advice on this page: <https://www.ory.sh/docs/kratos/guides/multi-domain-cookies>

When would someone need it?

I'm guessing one reason might be so oathkeeper can access the cookie on different subdomains?

So other services like a backend will be sent the cookie so they can introspect/authenticate the user

by setting the domain broader all subdomains will be sent the cookie allowing services on these domain to auth the user