Hi. That’s a great topic. Absolutely worth bringing it up at the IETF124 meeting if the agenda allows. From my perspective, the plateau in HTTP/3 adoption comes down to four main groups of issues:
1. UDP/443 blocked by misconfiguration or conservative policies. This is similar to the "disable IPv6 to fix problems" mindset. Some operators block QUIC traffic out of caution, even when doing so causes more harm than good. 2. Website owners are reluctant to enable HTTP/3. Brought to you by "if it isn’t broken, don’t fix it". Operators may fear regressions or simply prioritise other work since TCP-based HTTP already "works fine". 3. SNI-based filtering without QUIC support Many traffic filtering solutions that rely on SNI inspection do not support QUIC, so their operators default to blocking UDP/443. This is particularly visible on restricted networks such as guest Wi-Fis, which often only allow TCP/80, TCP/443, and UDP/53. I don't think IETF or QUIC WG should be doing anything to help passive SNI filtering. 4. Enterprise traffic inspection (NGFWs and proxies) While some products support QUIC inspection, major browsers deliberately downgrade to TCP/TLS when encountering certificates outside the Web PKI. Chromium has enforced this since 2019 [1], and Firefox since 2024 [2]. In Firefox it’s an advanced preference (network.http.http3.disable_when_third_party_roots_found), in Chromium it is hard-coded. This effectively excludes many enterprise deployments that rely on local trust anchors. Changing that unconfigurable behaviour to a setting easily adjustable in managed environments would go a long way. Looking forward, I see two broad levers to move adoption beyond the current plateau: Education and awareness. Helping operators understand that "HTTP/3 and IPv6 are your friends" could avoid unnecessary blocking. A browser-side UX nudge (such as showing a subtle “this site could be faster” indicator when HTTP/3 isn’t used) might also help. Unique capabilities. Wider deployment of features that are only possible with QUIC, such as WebTransport or Multipath QUIC, will make the benefits tangible for developers and users. But this requires more implementation work and easy-to-use APIs before it will drive adoption at scale. For IPv6, regulatory or procurement pressures have been an important driver of adoption. In contrast, I don’t expect a similar external push to accelerate migration to HTTP/3 / QUIC. Best Regards, Yaroslav [1] https://issues.chromium.org/issues/40634582 [2] https://bugzilla.mozilla.org/show_bug.cgi?id=1929368 On Mon, Sep 29, 2025 at 4:38 AM Lars Eggert <[email protected]> wrote: > Hi, > > pitch for a discussion at 124. > > https://radar.cloudflare.com/ > <https://radar.cloudflare.com/adoption-and-usage?dateRange=52w> and > similar stats have had H3 around 30% for a few years now, with little > changes since the first quichbram up to that level. > > Topic: why is that and is there anything the WG or IETF can do to change > it (upwards, of course)? > > Thanks, > Lars > -- > Sent from a mobile device; please excuse typos. > -- This communication (including any attachments) is intended for the sole use of the intended recipient and may contain confidential, non-public, and/or privileged material. Use, distribution, or reproduction of this communication by unintended recipients is not authorized. If you received this communication in error, please immediately notify the sender and then delete all copies of this communication from your system.
