SharedArrayBuffer messaging clarification

March 19, 2021

The Chrome team has announced that they are postponing the restriction on the SharedArrayBuffer object on desktop to Chrome 92 (originally Chrome 91). This change was made in response to feedback that the original message about this change was confusing.

You may have received an email from Google Search Console with the subject "New requirements for SharedArrayBuffers" if JavaScript on your website was using the SharedArrayBuffer object at the time the message was sent. The usage might be due to frameworks, libraries, or other third-party content included within your website.

For more information, please see the guide on enabling cross-origin isolation.

The SharedArrayBuffer is a JavaScript object that allows websites to share a memory space across threads. This was used before the Spectre vulnerability was found, but because Spectre is a CPU level vulnerability, browsers have decided to disable the SharedArrayBuffer object.

However, with the release of Chrome 92 planned for late May 2021, the SharedArrayBuffer object will be gated behind cross-origin isolation. This means that it will only be accessible to websites that are isolated from other sites. Firefox has already implemented this in version 76, and it is hoped that other browsers will follow suit soon.

The SharedArrayBuffer object is being deprecated in Chrome due to security concerns. You can determine where it is being used on your website using either Chrome DevTools or the Reporting API. Once you have determined which pages are affected, you can either remove the functionality or enable cross-origin isolation. If you are not sure what the SharedArrayBuffer object is, it is likely that a third-party resource on your website is using it. In this case, you should reach out to the resource provider and ask them to fix the issue.

After Chrome 92 is released, the SharedArrayBuffer object will no longer be functional without cross-origin isolation. In practice, this means that Chrome users on your site may experience degraded performance.

We hope this clarification was useful. If you have any questions, we recommend posting in the Search Central help community to get input from other experts.

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