In the coming weeks, Google Search for desktop will soon support signed exchanges for some sites. Sites serving different HTML based on the user-agent header (i.e. using dynamic serving) will need to opt out by adding a meta tag to your page.
Signed exchanges (SXG) allow Google Search to prefetch your content while preserving the user’s privacy. In practice, this means that both AMP and non-AMP results shown on Google Search may prefetch a few key resources (such as HTML, JavaScript, CSS, images, or fonts) in a privacy-preserving manner, if the associated website supports SXG, Google explained.
Google posted a notice about this in this Google Group this weekend saying “Google Search is planning to launch SXG support for desktop users in the coming weeks. Sites using responsive web design or separate mobile/desktop URLs don’t need to take action. Sites using dynamic serving (varying by User-Agent header) will need to annotate their pages as mobile- or desktop-only, as documented here. For example: Otherwise, desktop users may see the mobile version of the page.”
Google said it will be “reaching out individually to SXG sites who we’ve found to use dynamic serving, but I wanted a broad announcement in case there are any that we miss.”
This site still uses dynamic serving, so I wonder if we will get this notice or not? I might just wait and not do anything to see if we trigger an alert.
Devin Mullins from Google posted more about this on Twitter (hat tip @si1very):
Google Search will be rolling out desktop support for signed exchanges soon. For almost all sites, no action is needed. Sites serving different HTML based on the User-Agent header will need to opt out by adding a meta tag to your page: https://t.co/alCpVBKQIV
— Devin Mullins (@twifkak) April 23, 2022
and ICYMI, a recently published step-by-step guide to measuring and optimizing SXG performance improvement: https://t.co/DGH4j9vCJU
— Devin Mullins (@twifkak) April 23, 2022
You can see the details on the meta tags over here:
I wonder when Google will start notifying sites about this and I suspect most will want to add the meta tag if they are using dynamic serving?
Forum discussion at Twitter.