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SameSite Updates

Launch Timeline

Last updated Mar 18, 2021.

Latest update:

Mar 18, 2021: The flags #same-site-by-default-cookies and #cookies-without-same-site-must-be-secure have been removed from chrome://flags as of Chrome 91, as the behavior is now enabled by default. In Chrome 94, the command-line flag --disable-features=SameSiteByDefaultCookies,CookiesWithoutSameSiteMustBeSecure will be removed.

For the full Chrome release schedule, see here. For the SameSite-by-default and SameSite=None-requires-Secure launch timeline, see below:

The new SameSite behavior will not be enforced on Android WebView until later, though app developers are advised to declare the appropriate SameSite cookie settings for Android WebViews based on versions of Chrome that are compatible with the None value, both for cookies accessed via HTTP(S) headers and via Android WebView's CookieManager API. [UPDATE Jan 8, 2021: The modern SameSite behavior (SameSite=Lax by default, SameSite=None requires Secure, and Schemeful Same-Site) will be enabled by default for Android WebView on apps targeting Android 12 and newer. Existing apps will not be affected until they choose to update to target Android 12. Android 12 has not yet been released. Existing apps can be tested with the new modern SameSite behavior by toggling the flag webview-enable-modern-cookie-same-site in the developer UI.] This does not apply to Chrome browser on Android, which will begin to enforce the new SameSite rules at the same time as the desktop versions of Chrome. The new SameSite behavior will not affect Chrome on iOS.

All updates:

Mar 18, 2021

The flags #same-site-by-default-cookies and #cookies-without-same-site-must-be-secure have been removed from chrome://flags as of Chrome 91, as the behavior is now enabled by default. In Chrome 94, the command-line flag --disable-features=SameSiteByDefaultCookies,CookiesWithoutSameSiteMustBeSecure will be removed.

Jan 8, 2021

The modern SameSite behavior (SameSite=Lax by default, SameSite=None requires Secure, and Schemeful Same-Site) will be enabled by default for Android WebView on apps targeting Android 12 (Android S) and newer. Existing apps will not be affected until they choose to update to target Android 12. Android 12 has not yet been released. Existing apps can be tested with the new modern SameSite behavior by toggling the flag webview-enable-modern-cookie-same-site in the developer UI.

Aug 11, 2020

The target rollout population has been increased to 100% of users on Chrome Stable versions 80 and above, and the actual proportion of users with the new behavior enabled is now ramping up to 100% gradually. Users will receive the new behavior when they restart Chrome.

July 28, 2020

The rollout population has been increased to target a fraction of the overall Chrome 80+ stable population. We are monitoring metrics and ecosystem feedback on our tracking bug.

July 14, 2020

SameSite cookie enforcement has resumed, with a gradual rollout starting today (July 14) and ramping up over the next several weeks as we continue to monitor overall ecosystem readiness and engage with websites and services to ensure they are prepared for the SameSite labeling policy. The SameSite features are being enabled for Chrome Stable channel users on versions 80 and 81 (who should update Chrome!), 83, as well as the newly released 84.

May 28, 2020

We are planning to resume our SameSite cookie enforcement coinciding with the stable release of Chrome 84 on July 14, with enforcement enabled for Chrome 80+. (In other words, starting July 14, Chrome users on the older Stable releases (80, 81, and 83 -- for whom we recommend installing the latest update!) as well as the newly released Chrome 84 will gradually begin to receive the SameSite-by-default behavior.) Read more on our Chromium blog post.

April 3, 2020

We’ve decided to temporarily roll back the enforcement of SameSite cookie labeling on Chrome 80 Stable and kSameSiteByDefaultCookies is once again set to base::FEATURE_DISABLED_BY_DEFAULT in Chromium master.

Feb 10, 2020

The Chrome policies LegacySameSiteCookieBehaviorEnabledForDomainList and LegacySameSiteCookieBehaviorEnabled which revert to the legacy cookie behavior for managed Chrome and ChromeOS instances will be available for at least 12 months after the release of Chrome 80 stable (Edit - May 29, 2020: until at least July 14, 2021). We will be monitoring feedback about these policies and will provide updates on their lifetime as appropriate.

Nov 21, 2019

Starting in Canary version 80.0.3975.0, the Lax+POST temporary mitigation can be disabled for testing purposes using the new flag --enable-features=SameSiteDefaultChecksMethodRigorously to allow testing of sites and services in the eventual end state of the feature where the mitigation has been removed. (Note that to enable multiple features, you must append the feature name to the comma-separated list of params for the --enable-features flag. Do not use multiple separate --enable-features flags.)

In addition, there is a bug affecting Chrome 78-79 which causes spurious SameSite warning messages to be emitted to the console when the user has cookies for other domains on the same site as a resource fetched in a cross-site context. We apologize for the confusion. This will be fixed in Chrome 80.

Nov 1, 2019

Clearing up some misconceptions and providing additional information about "Lax

Oct 2, 2019

In response to feedback from users and enterprise customers, we are deferring the experimental Beta launch of the "SameSite=Lax by Default" and "SameSite=None requires Secure" features from Chrome 78 Beta to Chrome 79 Beta. Users of Chrome 78 Beta will not experience any change or disruption in cookie behavior.

When the experiment is launched to Chrome 79 Beta users, domain-joined or enterprise-registered machines will be included in the experiment. Instead of excluding them from the experiment entirely, policies will be made available in Chrome 79 to manage the experimental behavior. This will provide extra time for administrators to configure and test the policies in advance of the Stable launch in Chrome 80.

One policy will allow administrators to specify a list of domains on which cookies should be handled according to the legacy behavior (LegacySameSiteCookieBehaviorEnabledForDomainList), and a second policy will provide the option to set the global default to legacy SameSite behavior for all cookies (LegacySameSiteCookieBehaviorEnabled). More details about these policies will follow in future enterprise release notes before the Chrome 79 release.

These features will still become the default behavior on Stable starting in Chrome 80.

Sept 30, 2019

Note (Jan 30, 2020): Check out our more detailed tips for testing and debugging.

To test whether your sites may be affected by the SameSite changes:

Go to chrome://flags and enable #same-site-by-default-cookies and
#cookies-without-same-site-must-be-secure. Restart the browser for the
changes to take effect.

Test your sites, with a focus on anything involving federated login flows,
multiple domains, or cross-site embedded content. Note that, because of the
2 minute time threshold for the "Lax+POST" intervention, for any flows
involving POST requests, you may want to test with and without a long (>
2 minute) delay.

If your site stops working:

*   Try turning off #cookies-without-same-site-must-be-secure. If
            this fixes the issue, you need to set \`Secure\` on any
            \`SameSite=None\` cookies your site may be relying upon. (This
            may require upgrading HTTP sites to HTTPS.)
*   Try turning off both flags. If this fixes the issue, you need to
            identify the cookies being accessed in a cross-site context and
            apply the attributes \`SameSite=None\` and \`Secure\` to them.
            See ["SameSite cookies
            explained"](https://web.dev/samesite-cookies-explained/) for
            more information. If you are not the developer of the site,
            please reach out to the developer and/or vendor who authored the
            site.
*   For flows involving POST requests, if a short delay (< 2
            minutes) works but a long delay (> 2 minutes) does not work,
            you will also need to add \`SameSite=None\` and \`Secure\` to
            the relevant cookies if the operation in question may take
            longer than 2 minutes. Note that the 2-minute window for
            "Lax+POST" is a temporary intervention and will be removed at
            some point in the future (some time after the Stable launch of
            Chrome 80), at which point cookies involved in these flows will
            require \`SameSite=None\` and \`Secure\` even if under 2
            minutes.

If you are an IT administrator managing a Chrome deployment for your organization, policies will temporarily be made available to maintain Chrome's existing behavior for your users. This is to give enterprises extra time to roll out and test changes. You have two options:

  1. (Recommended) Apply the LegacySameSiteCookieBehaviorEnabledForDomainList policy to the specific domains on which cookies require legacy behavior.
  2. (Less recommended due to security and privacy implications) Apply the LegacySameSiteCookieBehaviorEnabled policy to revert all cookies to legacy behavior.

These policies will be made available starting in Chrome 80. Chrome 79. (See Oct 2, 2019 update.)

Sept 26, 2019

Starting in Chrome 80, cookies that do not specify a SameSite attribute will be treated as if they were SameSite=Lax with the additional behavior that they will still be included in POST requests to ease the transition for existing sites. Cookies that still need to be delivered in a cross-site context can explicitly request SameSite=None, and must also be marked Secure and delivered over HTTPS. We will provide policies if you need to configure Chrome Browser to temporarily revert to legacy SameSite behavior.

This section is obsolete: See Oct 2, 2019 update.

While experiments for this change will be rolling out to Chrome 78 Beta users, the Beta SameSite experiment rollout will exclude Windows and Mac devices that are joined to a domain and Chrome OS devices that are enterprise-registered. Beta users on Linux, iOS, Android, and Android Webview will also not be affected by the experiments at this time. For Chrome Beta users unaffected by the experiments, there should be no change in behavior to login services or embedded content.

The new SameSite rules will become the default behavior on Stable in Chrome 80, but the changes will be limited to pre-Stable versions of Chrome until then.

Policies to manage this behavior will be made available when it becomes the default behavior for Chrome 80. One policy will allow administrators to specify a list of domains on which cookies should be handled according to the legacy behavior, and second policy will provide the option to set the global default to legacy SameSite behavior for all cookies. More details about these policies will follow in future enterprise release notes before the Chrome 80 release.

Chrome continues to engage with members of the web community and welcomes input on these SameSite changes via our forum: https://groups.google.com/a/chromium.org/forum/#!forum/blink-dev