Comparison
CookievsThird-party cookie
Cookie
the value went out with every single request to that domain, whether it was needed or not.
A small piece of data the browser stores and attaches automatically to matching requests. That automatic attachment is the entire difference from other storage: it is what makes cookies work for sessions and what makes them cost bytes on every request. Size limits are small, the attributes controlling scope and security are numerous, and the ones that matter are `HttpOnly`, `Secure` and `SameSite`.
Full entry →Third-party cookie
the embedded iframe could not read its own cookie because it was not the site in the address bar.
A cookie set by an origin other than the one in the address bar, historically the mechanism behind cross-site tracking and behind most embedded session flows. Browsers have been restricting and partitioning them for years, so any feature relying on one is on a deadline. The replacements — storage partitioning, dedicated APIs, first-party redirect flows — all require the embedded product to change.
Full entry →