SameSiteattributen

SameSiteattributen refers to the SameSite cookie attribute, a property that controls when cookies are sent with cross-origin requests. It is used to improve privacy and security by reducing the risk of cross-site request forgery (CSRF). The attribute can take three values: Strict, Lax, and None.

Cookies with SameSite=Strict are only sent in requests that originate from the same site as the cookie. This provides the strongest protection but can break cross-site workflows. SameSite=Lax allows cookies to be sent with top-level navigation to the site from a different origin, but not with most cross-site subrequests such as images or iframes. SameSite=None permits the cookie to be sent with all requests, including cross-site ones, but the cookie must also be marked Secure, meaning it will only be sent over HTTPS.

How the attribute works in practice: when a request is made, the browser checks the site context and whether the cookie’s SameSite value permits inclusion. Domain and path still determine whether a cookie is applicable. HttpOnly cookies remain inaccessible to client-side scripts, while SameSite governs when those cookies are included in requests.

Implementation and compatibility: in recent years, major browsers have tightened handling of SameSite. Cookies without a SameSite attribute are treated as Lax by default in many browsers, and SameSite=None cookies must be Secure. Developers should verify behavior across browsers and ensure Secure is set when using None, especially for cross-site functionality such as third-party integrations or single sign-on.

Practical guidance: set SameSite to Strict for highly sensitive cookies, or Lax for general session cookies, and use None only when cross-origin access is required and Secure is enabled. Always test cookie behavior in real cross-site scenarios and consider additional CSRF protections where appropriate.