No Accept-CH Client Hints header (opt-in, ~10% adoption)

Client Hints is an opt-in browser feature where your server can request extra information about a visitor's device — such as screen resolution and network speed — so it can send a more appropriately sized image or resource. For most sites this is a low-priority optimisation, with adoption still below 15% of the web. Image-heavy sites (portfolios, e-commerce, media) can see modest page-speed improvements on mobile by pairing Client Hints with an image CDN that uses the data. If your site is image-heavy and you already use an image CDN (such as Cloudflare Images, Imgix, or Cloudinary), ask your developer to add an Accept-CH response header listing the hints you want. Otherwise, this finding can be safely deprioritised.