This binary was built without support for HTTP/3. Enable…

Error message

This binary was built without support for HTTP/3. Enable the `http3` feature.

What it means

The user requested HTTP/3 prior knowledge but the binary was compiled without the `http3` cargo feature, so the QUIC/HTTP-3 transport code does not exist. The CLI tells the user which feature flag enables it.

Solutions

Remove the --http3 / HTTP/3 version option and use HTTP/2 or default negotiation.
Rebuild with the feature: cargo build --features http3 (requires a nightly-capable quinn stack per docs).
Obtain a binary release built with http3 support.
Verify server actually requires HTTP/3; most servers accept HTTP/2 or /1.1.

Example fix

// before
xh --http3 GET example.org
// after
cargo install xh --features http3
xh --http3 GET example.org

Defensive patterns

Strategy: fallback

Validate before calling

// shell guard: only request http3 if the build supports it
xh --http3 --check-all 2>/dev/null || flags_without_http3

Try / catch

match run(args) {
    Err(e) if e.to_string().contains("without support for HTTP/3") => {
        args.http_version = None; // fall back to negotiated version
        run(args)
    }
    other => other,
}

Prevention

Detect feature support before forcing HTTP/3 in scripts.
Rely on ALPN negotiation instead of prior-knowledge HTTP/3.
Pin builds with --features http3 where HTTP/3 is required.
Keep a fallback HTTP/2 path for minimal binary distributions.

When it happens

Trigger: run() handles Some(HttpVersion::Http3PriorKnowledge) under #[cfg(not(feature = "http3"))].

Common situations: Passing --http3 (or setting HTTP version to 3) with a standard release binary built without http3; distro packages that exclude experimental HTTP/3; scripts ported from machines with http3-enabled builds.

Related errors

AI-assisted analysis of ducaale/xh@2404aceecc (2026-09-13). Data as JSON: /api/errors/3b2fcc68b5fc6d17. Report an issue: GitHub.

Appendix: source

Thrown at src/main.rs:300

            Proxy::All(url) => reqwest::Proxy::all(url),
        }?);
    }

    client = match args.http_version {
        Some(HttpVersion::Http10 | HttpVersion::Http11) => client.http1_only(),
        Some(HttpVersion::Http2PriorKnowledge) => client.http2_prior_knowledge(),
        Some(HttpVersion::Http2) => client,
        Some(HttpVersion::Http3PriorKnowledge) => {
            #[cfg(feature = "http3")]
            {
                if args.native_tls {
                    return Err(anyhow!("HTTP/3 is not supported when using native-tls"));
                }
                client.http3_prior_knowledge()
            }
            #[cfg(not(feature = "http3"))]
            {
                return Err(anyhow!(
                    "This binary was built without support for HTTP/3. Enable the `http3` feature."
                ));
            }
        }
        None => client,
    };

    let cookie_jar = Arc::new(reqwest_cookie_store::CookieStoreMutex::default());
    client = client.cookie_provider(cookie_jar.clone());

    client = match (args.ipv4, args.ipv6) {
        (true, false) => client.local_address(IpAddr::from(Ipv4Addr::UNSPECIFIED)),
        (false, true) => client.local_address(IpAddr::from(Ipv6Addr::UNSPECIFIED)),
        _ => client,
    };

    if let Some(name_or_ip) = &args.interface {
        if let Ok(ip_addr) = IpAddr::from_str(name_or_ip) {

View on GitHub (pinned to 2404aceecc)