Google Search Console Is Sending out Email Notifications About SharedArrayBuffer

Message Reads

New requirements for SharedArrayBuffers on <>
Google systems have recently detected that SharedArrayBuffers (SABS) are used on <>, but COOP and/or COEP headers are not served.

For Web Compatibility reasons Chrome is planning to require COOP/COEP for the use of SABs from Chrome 91 (2021-05-25) onwards. Please implement ‘cross-origin-isolated’ behavior on your site.

You can learn more about them from their help documentation and this help doc.

Update 22/03/2021: Google is adding some more info on why you got this email and how you can fix it in their help documentation.