I work on a developer tool called PWABuilder, which helps developers build Progressive Web Apps (PWAs).
Cloudflare’s HTTP/3 support has been giving me many headaches lately.
Specifically, I use various backend services to fetch website content (manifests, service workers, images, and more). But most HTTP APIs – including those in Node, .NET, and Java – don’t currently support HTTP/3, as it’s still an experimental protocol.
What ends up happening is developers open issues asking why their sites aren’t working with my developer tools. I investigate, only to find that their sites are being served via Cloudflare’s experimental HTTP/3 support, often unknowingly.
Is there a way during my HTTP fetch calls to tell Cloudflare not to serve HTTP/3 requests? Request headers perhaps or some other way? I assume that Cloudflare can gracefully handle cases where HTTP/3 isn’t supported and fallback to HTTP/2 or 1.1. But I don’t see a way to advertise that to Cloudflare while making my programmatic HTTP fetch calls.