HTTP/3 across CDNs in 2026: who actually turns it on
Of the 104 hosts in our sample advertising HTTP/3 support, 62 are served by Cloudflare. Every other CDN and hand-configured server combined accounts for 42.
The difference is decisive: behind Cloudflare 67–82% of sites advertise support, outside it 5–18%. And that fully explains why HTTP/3 is rare in the Russian web: Cloudflare serves 3.6% of sites there against 28.7% in .com.
Free online tool — health checker: instant results, no signup.
Two thirds of HTTP/3 advertisers are one CDN
On 27 August 2026 we requested 600 hosts over HTTPS and checked which advertise HTTP/3 support via the alt-svc header. There were 104. By what serves them:
| Server or CDN | .ru | .com | .net | .org | Total |
|---|---|---|---|---|---|
| Cloudflare | 3 | 27 | 14 | 18 | 62 |
| nginx (own server) | 2 | 4 | 1 | 4 | 11 |
| Unnamed | 1 | 1 | 4 | 2 | 8 |
| LiteSpeed | 1 | 2 | 0 | 0 | 3 |
| DDoS-Guard | 0 | 1 | 1 | 1 | 3 |
| Amazon CloudFront | 0 | 1 | 1 | 0 | 2 |
| Caddy | 1 | 0 | 1 | 0 | 2 |
| Google, Akamai, Apache | 0 | 1 | 1 | 1 | 3 |
| Others | 0 | 5 | 3 | 2 | 10 |
62 of 104 are Cloudflare. Everything else combined — CloudFront, Google, Akamai, and hand-configured nginx and Caddy — accounts for 42.
Behind Cloudflare, HTTP/3 is advertised four times more often
Comparing the share advertising h3 behind Cloudflare against outside it:
| Zone | Behind Cloudflare | Outside it | Ratio |
|---|---|---|---|
| .com | 27 of 33 — 82% | 15 of 82 — 18% | 4.5× |
| .net | 14 of 18 — 78% | 12 of 76 — 16% | 4.9× |
| .org | 18 of 27 — 67% | 10 of 82 — 12% | 5.5× |
| .ru | 3 of 4 — 75% | 5 of 108 — 5% | 16× |
The pattern is the same in every zone: sitting behind Cloudflare means roughly a three-in-four chance of getting HTTP/3 automatically, while outside it support is rare.
A caveat on the .ru row: only four sites there sit behind Cloudflare. The 75% is computed on four and carries no independent weight — it is shown only to indicate the mechanism is the same. What is solid in that row is the right-hand side: 5 of 108 outside Cloudflare.
Why HTTP/3 is rare in the Russian web — and it is not the administrators
Cloudflare’s presence itself differs by an order of magnitude across zones:
| Zone | Responded | Behind Cloudflare | Share |
|---|---|---|---|
| .com | 115 | 33 | 28.7% |
| .org | 109 | 27 | 24.8% |
| .net | 94 | 18 | 19.1% |
| .ru | 112 | 4 | 3.6% |
Which fully explains the HTTP/3 gap we measured separately (7.1% in .ru against 36.5% in .com): it is not that Russian administrators fail to enable HTTP/3, but that they do not sit behind the CDN that enables it for them.
The point is supported outside Cloudflare too: there .ru gives 5% against 12–18% in the international zones. A gap remains, but threefold rather than fivefold, explained by other CDNs also being rarer in the Russian web.
A second independent source says the same. Per the Web Almanac (July 2025 crawl), mobile HTML delivered through a CDN went over HTTP/3 in 29% of cases; delivered straight from the origin, in 0%.
What to do when a CDN is not an option
HTTP/3 can be enabled on your own server — our measurement found eleven such on nginx and two on Caddy. The order of work:
- Check the version. nginx gained QUIC support in the 1.25 branch, and the build needs a suitable TLS library. Caddy has HTTP/3 on by default.
- Open UDP port 443. This is the commonest reason everything is configured and nothing works: HTTP/3 runs over UDP, and a TCP firewall rule will not pass it.
- Send the
alt-svcheader. Without it a browser never learns of the support and stays on HTTP/2 — a server can speak HTTP/3 and receive not one connection over it. - Do not expect miracles from speed. HTTP/3’s benefit lands on poor and mobile connections where packets are lost. On a fast wired link the difference from HTTP/2 is usually imperceptible.
To check what your site actually sends, use the protocol test.
Why teams trust us
How it works
Enter site URL
Analyse 10+ factors
Get overall score
What is Health Score?
Health Score is a comprehensive assessment of site technical health across 20+ parameters: SSL, security headers, response speed, SEO technical factors, and availability.
Comprehensive Score
20+ parameters in one number: SSL, headers, speed, SEO technical factors.
Detailed Breakdown
Each parameter with explanation — what is checked, what was found, how to fix.
Score Trends
Compare Health Score at different dates — see progress or regression.
Health Monitoring
Set up automated Health Score checks and get notified when the score drops.
Who uses this
Developers
quick pre-release audit
SEO
technical baseline score
Marketers
client site check
Security
header security audit
Common Mistakes
Best Practices
Get more with a free account
Health Score check history and real-time site health monitoring.
Sign up freeLearn more
Frequently Asked Questions
When will HTTP/3 become default everywhere?
2027-2028 based on trends. AWS CloudFront — the key blocker, 35 % CDN market.
Overhead?
QUIC userspace cipher = higher CPU. Cloudflare reports +5-10 % CPU vs TLS-over-TCP.
How to test?
enterno.io/protocol-test — checks HTTP/1.1, HTTP/2, HTTP/3 support on any URL.
Try the live tool that powered this guide
Free plan — 10 monitors, checks every 5 min, no card required. Upgrade for 1-minute interval and multi-region monitoring.