Introducing HTTP/3 Prioritization

What this post added

Introduced full support for HTTP/3 Extensible Priorities (RFC 9218), a new standard for web page loading optimization. This feature allows clients to signal request urgency and incremental processing, enabling Cloudflare's network to prioritize and schedule response data for improved performance, with observed Largest Contentful Paint (LCP) improvements of up to 37%. The post details the 'urgency' and 'incremental' parameters, how they are signaled via HTTP headers and PRIORITY_UPDATE frames, and Cloudflare's server-side scheduling recommendations based on these signals. It also provides examples of how server-side overrides can be used with Cloudflare Workers or origins to customize prioritization behavior.