boring-http

An asyncio HTTP client on BoringSSL through ssl2 and boring-ssl2. HTTP/1.1, HTTP/2 and HTTP/3 over QUIC v1 and v2, WebSocket on all three, HTTP and SOCKS proxies, headers sent in the order you give them, cookies, redirects, phased timeouts, gzip, deflate, brotli and zstd decoding. Runs on asyncio and on uvloop. Requires Python 3.14.

uv add boring-http

Requests

import asyncio

from boring_http import Client, Http2Settings
from ssl2 import AkamaiFingerprint

http2 = Http2Settings(AkamaiFingerprint.parse("1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p"))


async def main() -> None:
    async with Client(http2=http2, headers=[("User-Agent", "boring-http/0.1"), ("Accept", "application/json")]) as client:
        response = await client.get("https://pingly.us.kg/api/all", params={"page": 2})
        print(response.status, response.version, response.content_type)  # 200 h2 application/json
        report = response.json()
        print(report["http_version"], report["user_agent"], report["method"])  # HTTP/2.0 boring-http/0.1 GET

        response = await client.post("https://httpbingo.org/post", json={"name": "boring"}, headers=[("X-Trace", "abc")])
        echoed = response.json()
        print(echoed["json"], echoed["headers"]["X-Trace"])  # {'name': 'boring'} ['abc']


asyncio.run(main())

Certificates are checked against the system trust store, or against trust_store=TrustStore.from_file(...) from ssl2; verify=False turns the check off for a test server. Revocation is checked against the CRL the certificate names: fetched over HTTP, verified with the issuer from the chain, cached until its next update, and a listed certificate is refused with RevocationError. revocation=Revocation.STRICT also refuses when no valid CRL can be had, Revocation.NONE skips the check, and the default Revocation.SOFT lets such a connection through, as browsers do. The check covers the origin's certificate and an HTTPS proxy's own certificate on a plain-HTTP request through it; the proxy's certificate on a TLS tunnel is verified but not checked for revocation. Headers go on the wire in the order given, client headers first and then the request's own. Host leads an HTTP/1.1 request; HTTP/2 and HTTP/3 lowercase the names and drop the connection-specific ones, nothing else changes. params, json, data, content, files, auth and cookies are accepted by get, post, put, patch, delete, head, options and request.

Responses

import asyncio

from boring_http import Client, Http2Settings
from ssl2 import AkamaiFingerprint

http2 = Http2Settings(AkamaiFingerprint.parse("1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p"))


async def main() -> None:
    async with Client(http2=http2) as client:
        response = await client.get("https://httpbingo.org/redirect/2")
        print(response.status, response.url.path, [step.status for step in response.history])  # 200 /get [302, 302]

        response = await client.get("https://httpbingo.org/redirect/1", allow_redirects=False)
        print(response.status, response.is_redirect, response.location.path)  # 302 True /get

        response = await client.get("https://httpbingo.org/cookies/set?flavor=plain", allow_redirects=False)
        print([cookie.name for cookie in response.cookies], client.cookies.header("httpbingo.org", "/", True))  # ['flavor'] flavor=plain


asyncio.run(main())

response.cookies holds only the cookies this response set; client.cookies is the jar that follows every request. location, content_type, charset, content_length, content_encoding, retry_after, etag, last_modified and date are parsed, response.headers keeps the raw fields in order, raise_for_status() raises HTTPStatusError.

Streaming and timeouts

import asyncio

from boring_http import Client, Http2Settings, Timeout, TimeoutError
from ssl2 import AkamaiFingerprint

http2 = Http2Settings(AkamaiFingerprint.parse("1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p"))


async def main() -> None:
    async with Client(http2=http2, timeout=Timeout(connect=5, read=10, write=10, total=30)) as client:
        async with client.stream("GET", "https://httpbingo.org/stream-bytes/100000") as response:
            size = sum([len(chunk) async for chunk in response.aiter_bytes()])
        print(response.status, size)  # 200 100000

        try:
            await client.get("https://httpbingo.org/delay/3", timeout=0.5)
        except TimeoutError as error:
            print(error.phase, error)  # total total timed out after 0.5 seconds


asyncio.run(main())

A single number sets every phase and the total, so the request gives up after that many seconds whatever it was doing. With a Timeout the phases are separate: read is the longest wait for the next bytes, total caps the whole exchange including redirects, and the error names whichever ran out.

HTTP/3

import asyncio
from dataclasses import replace

from boring_http import Client, Http2Settings, Http3Settings, Parameter, QuicVersion, Setting, TransportParameters
from ssl2 import AkamaiFingerprint, PseudoHeader

http2 = Http2Settings(AkamaiFingerprint.parse("1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p"))
http3 = Http3Settings(
    settings=((Setting.QPACK_MAX_TABLE_CAPACITY, 65536), (Setting.MAX_FIELD_SECTION_SIZE, 262144), (Setting.QPACK_BLOCKED_STREAMS, 100)),
    pseudo_header_order=(PseudoHeader.METHOD, PseudoHeader.AUTHORITY, PseudoHeader.SCHEME, PseudoHeader.PATH),
    transport=TransportParameters(
        max_idle_timeout=30000,
        max_udp_payload_size=1472,
        initial_max_data=15728640,
        initial_max_stream_data_bidi_local=6291456,
        initial_max_stream_data_bidi_remote=6291456,
        initial_max_stream_data_uni=6291456,
        initial_max_streams_bidi=100,
        initial_max_streams_uni=100,
        order=(
            Parameter.MAX_IDLE_TIMEOUT,
            Parameter.MAX_UDP_PAYLOAD_SIZE,
            Parameter.INITIAL_MAX_DATA,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_LOCAL,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_REMOTE,
            Parameter.INITIAL_MAX_STREAM_DATA_UNI,
            Parameter.INITIAL_MAX_STREAMS_BIDI,
            Parameter.INITIAL_MAX_STREAMS_UNI,
            Parameter.INITIAL_SOURCE_CONNECTION_ID,
            Parameter.VERSION_INFORMATION,
        ),
    ),
)


async def main() -> None:
    async with Client(versions=("h3", "h2", "h1"), http2=http2, http3=http3) as client:
        first = await client.get("https://pingly.us.kg/api/all")
        second = await client.get("https://pingly.us.kg/api/all")
        print(first.version, second.version)  # h2 h3, the Alt-Svc header taught the client that this origin speaks HTTP/3

    async with Client(versions=("h3",), http3=replace(http3, quic_version=QuicVersion.V2)) as client:
        response = await client.get("https://pingly.us.kg/api/all")
        print(response.version, response.json()["http_version"])  # h3 HTTP/3.0


asyncio.run(main())

The default is versions=("h2", "h1"). With "h3" in the list the client switches an origin to QUIC after an Alt-Svc: h3 header and falls back to TCP when the QUIC route stops answering; versions=("h3",) goes straight to QUIC. QUIC v1 is the default; quic_version=QuicVersion.V2 offers v2 through compatible version negotiation (RFC 9368), so the first packet is still v1 and a server that speaks v2, such as aioquic, ngtcp2, haproxy or haskell quic, switches to it, while every other server simply stays on v1; v2 needs Parameter.VERSION_INFORMATION in order. Retry packets, version negotiation, loss recovery, pacing, flow control, key updates, path MTU probing from 1200 up to 1452 bytes with the don't-fragment flag set, QPACK with the dynamic table the SETTINGS allow on the decoding side and 0-RTT are handled; connection migration is not. A second connection to an origin resumes the TLS session and sends GET, HEAD and OPTIONS requests before the handshake has finished, under the limits and SETTINGS the server gave last time; other methods wait for the handshake, a 425 answer is retried after it, and a server that declines the early data gets it again under the 1-RTT keys. TransportParameters sends the parameters in order, in that order, and refuses a value the peer would never see: one that differs from the RFC's absent value, or a GREASE version, connection options or round trip time, with its parameter missing from order. max_idle_timeout=0 sets no idle timeout. grease=True adds a GREASE entry, grease_version=True a GREASE version, shuffle=True a fresh random order on every connection, and INITIAL_ROUND_TRIP_TIME in order sends initial_round_trip_time, or else the round trip time measured on the last connection to that origin. The control stream carries the SETTINGS of the Http3Settings, a GREASE entry and a GREASE frame with grease=True, and a PRIORITY_UPDATE for every request that has a priority header.

Proxies

import asyncio

from boring_http import Client, Http2Settings, Http3Settings, Parameter, Setting, TransportParameters
from ssl2 import AkamaiFingerprint, ProxyError, PseudoHeader

http2 = Http2Settings(AkamaiFingerprint.parse("1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p"))
http3 = Http3Settings(
    settings=((Setting.QPACK_MAX_TABLE_CAPACITY, 65536), (Setting.MAX_FIELD_SECTION_SIZE, 262144), (Setting.QPACK_BLOCKED_STREAMS, 100)),
    pseudo_header_order=(PseudoHeader.METHOD, PseudoHeader.AUTHORITY, PseudoHeader.SCHEME, PseudoHeader.PATH),
    transport=TransportParameters(
        max_idle_timeout=30000,
        max_udp_payload_size=1472,
        initial_max_data=15728640,
        initial_max_stream_data_bidi_local=6291456,
        initial_max_stream_data_bidi_remote=6291456,
        initial_max_stream_data_uni=6291456,
        initial_max_streams_bidi=100,
        initial_max_streams_uni=100,
        order=(
            Parameter.MAX_IDLE_TIMEOUT,
            Parameter.MAX_UDP_PAYLOAD_SIZE,
            Parameter.INITIAL_MAX_DATA,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_LOCAL,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_REMOTE,
            Parameter.INITIAL_MAX_STREAM_DATA_UNI,
            Parameter.INITIAL_MAX_STREAMS_BIDI,
            Parameter.INITIAL_MAX_STREAMS_UNI,
            Parameter.INITIAL_SOURCE_CONNECTION_ID,
            Parameter.VERSION_INFORMATION,
        ),
    ),
)


async def main() -> None:
    async with Client(http2=http2, proxy="socks5h://alice:secret@127.0.0.1:1080") as client:
        response = await client.get("https://pingly.us.kg/api/all")  # SOCKS5 CONNECT, HTTP/2 inside
        print(response.version, response.json()["http_version"])  # h2 HTTP/2.0
        response = await client.get("https://pingly.us.kg/api/all", proxy="http://alice:secret@127.0.0.1:3128")  # per request
        print(response.version)  # h2

    async with Client(versions=("h3",), http3=http3, proxy="socks5h://alice:secret@127.0.0.1:1080") as client:
        response = await client.get("https://pingly.us.kg/api/all")  # SOCKS5 UDP ASSOCIATE, QUIC datagrams through the relay
        print(response.version, response.json()["http_version"])  # h3 HTTP/3.0

    try:
        async with Client(http2=http2, proxy="socks5h://alice:wrong@127.0.0.1:1080") as client:
            await client.get("https://pingly.us.kg/api/all")
    except ProxyError as refusal:
        print(refusal)  # the SOCKS5 proxy rejected the username and password


asyncio.run(main())

http://, https://, socks4://, socks4a://, socks5:// and socks5h:// proxies, with credentials in the URL. HTTP and SOCKS proxies carry HTTP/1.1 and HTTP/2; SOCKS5 also carries HTTP/3. proxy=None on a request bypasses the client's proxy.

Fingerprints

import asyncio

from boring_http import Client, Http2Settings
from ssl2 import (
    JA4,
    AkamaiFingerprint,
    CertificateCompressionAlgorithm,
    CipherSuite,
    ClientHelloBuilder,
    ECPointFormat,
    ExtensionType,
    Http2Priority,
    NamedGroup,
    NextProtocol,
    ProtocolVersion,
    PskKeyExchangeMode,
    SignatureScheme,
)

hello = (
    ClientHelloBuilder()
    .supported_versions(ProtocolVersion.TLS_1_3, ProtocolVersion.TLS_1_2)
    .cipher_suites(
        CipherSuite.TLS_AES_128_GCM_SHA256,
        CipherSuite.TLS_AES_256_GCM_SHA384,
        CipherSuite.TLS_CHACHA20_POLY1305_SHA256,
        CipherSuite.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
        CipherSuite.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
        CipherSuite.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
        CipherSuite.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
        CipherSuite.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
        CipherSuite.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
        CipherSuite.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
        CipherSuite.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
        CipherSuite.TLS_RSA_WITH_AES_128_GCM_SHA256,
        CipherSuite.TLS_RSA_WITH_AES_256_GCM_SHA384,
        CipherSuite.TLS_RSA_WITH_AES_128_CBC_SHA,
        CipherSuite.TLS_RSA_WITH_AES_256_CBC_SHA,
    )
    .extensions(
        ExtensionType.server_name,
        ExtensionType.extended_main_secret,
        ExtensionType.renegotiation_info,
        ExtensionType.supported_groups,
        ExtensionType.ec_point_formats,
        ExtensionType.session_ticket,
        ExtensionType.application_layer_protocol_negotiation,
        ExtensionType.status_request,
        ExtensionType.signature_algorithms,
        ExtensionType.signed_certificate_timestamp,
        ExtensionType.key_share,
        ExtensionType.psk_key_exchange_modes,
        ExtensionType.supported_versions,
        ExtensionType.compress_certificate,
        ExtensionType.application_settings,
        ExtensionType.encrypted_client_hello,
    )
    .supported_groups(NamedGroup.X25519MLKEM768, NamedGroup.x25519, NamedGroup.secp256r1, NamedGroup.secp384r1)
    .key_shares(NamedGroup.X25519MLKEM768, NamedGroup.x25519)
    .ec_point_formats(ECPointFormat.uncompressed)
    .signature_algorithms(
        SignatureScheme.ecdsa_secp256r1_sha256,
        SignatureScheme.rsa_pss_rsae_sha256,
        SignatureScheme.rsa_pkcs1_sha256,
        SignatureScheme.ecdsa_secp384r1_sha384,
        SignatureScheme.rsa_pss_rsae_sha384,
        SignatureScheme.rsa_pkcs1_sha384,
        SignatureScheme.rsa_pss_rsae_sha512,
        SignatureScheme.rsa_pkcs1_sha512,
    )
    .application_protocols(NextProtocol.H2, NextProtocol.HTTP1)
    .application_settings(NextProtocol.H2)
    .certificate_compression(CertificateCompressionAlgorithm.brotli)
    .psk_key_exchange_modes(PskKeyExchangeMode.psk_dhe_ke)
    .build()
)
http2 = Http2Settings(
    AkamaiFingerprint.parse("1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p"),
    headers_priority=Http2Priority(stream_id=0, exclusive=True, dependency=0, weight=256),
)


async def main() -> None:
    async with Client(tls=hello, http2=http2) as client:
        report = (await client.get("https://pingly.us.kg/api/all")).json()
        print(report["tls"]["ja4"] == JA4.of(hello).text, report["tls"]["ja4"])  # True t13d1516h2_8daaf6152771_d8a2da3f94cd
        print(report["http2"]["akamai_fingerprint"] == http2.fingerprint.text, report["http2"]["akamai_fingerprint"])  # True 1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p


asyncio.run(main())

Over HTTP/3 the same holds, with the ClientHello Chrome 155 sends on QUIC: TLS 1.3 only, the trust_anchors extension with the 28 identifiers of Chrome's root store, and pre_shared_key once a session exists.

import asyncio

from boring_http import Client, Http3Settings, Parameter, Setting, TransportParameters
from ssl2 import (
    JA4,
    CertificateCompressionAlgorithm,
    CipherSuite,
    ClientHelloBuilder,
    ExtensionType,
    JA4Transport,
    NamedGroup,
    NextProtocol,
    ProtocolVersion,
    PseudoHeader,
    PskKeyExchangeMode,
    SignatureScheme,
)

quic_hello = (
    ClientHelloBuilder()
    .supported_versions(ProtocolVersion.TLS_1_3)
    .cipher_suites(CipherSuite.TLS_AES_128_GCM_SHA256, CipherSuite.TLS_AES_256_GCM_SHA384, CipherSuite.TLS_CHACHA20_POLY1305_SHA256)
    .extensions(
        ExtensionType.signature_algorithms,
        ExtensionType.application_settings,
        ExtensionType.application_layer_protocol_negotiation,
        ExtensionType.compress_certificate,
        ExtensionType.trust_anchors,
        ExtensionType.server_name,
        ExtensionType.psk_key_exchange_modes,
        ExtensionType.key_share,
        ExtensionType.quic_transport_parameters,
        ExtensionType.supported_versions,
        ExtensionType.supported_groups,
        ExtensionType.encrypted_client_hello,
        ExtensionType.pre_shared_key,
    )
    .supported_groups(NamedGroup.X25519MLKEM768, NamedGroup.x25519, NamedGroup.secp256r1, NamedGroup.secp384r1)
    .key_shares(NamedGroup.X25519MLKEM768, NamedGroup.x25519)
    .signature_algorithms(
        SignatureScheme.ecdsa_secp256r1_sha256,
        SignatureScheme.rsa_pss_rsae_sha256,
        SignatureScheme.rsa_pkcs1_sha256,
        SignatureScheme.ecdsa_secp384r1_sha384,
        SignatureScheme.rsa_pss_rsae_sha384,
        SignatureScheme.rsa_pkcs1_sha384,
        SignatureScheme.rsa_pss_rsae_sha512,
        SignatureScheme.rsa_pkcs1_sha512,
        SignatureScheme.rsa_pkcs1_sha1,
    )
    .application_protocols(NextProtocol.H3)
    .application_settings(NextProtocol.H3)
    .certificate_compression(CertificateCompressionAlgorithm.brotli)
    .psk_key_exchange_modes(PskKeyExchangeMode.psk_dhe_ke)
    .trust_anchor_ids(
        "44947.2.1", "44947.2.6", "44947.2.13", "44947.2.14", "44947.2.15", "44947.2.18", "44947.2.19", "44947.2.20",
        "52580.200109.1.7", "52580.200109.1.8", "52580.200109.1.9", "52580.200109.1.10", "52580.200109.1.11", "52580.200109.1.12", "52580.200109.1.13", "52580.200109.1.18", "52580.200109.1.19",
        "11129.9.1", "11129.9.4", "11129.9.5", "11129.9.6", "11129.9.7", "11129.9.8", "11129.9.10", "11129.9.11", "11129.9.12", "11129.9.13", "11129.9.15",
    )
    .grease()
    .permute_extensions()
    .build()
)
http3 = Http3Settings(
    settings=((Setting.QPACK_MAX_TABLE_CAPACITY, 65536), (Setting.MAX_FIELD_SECTION_SIZE, 262144), (Setting.QPACK_BLOCKED_STREAMS, 100), (Setting.H3_DATAGRAM, 1)),
    pseudo_header_order=(PseudoHeader.METHOD, PseudoHeader.AUTHORITY, PseudoHeader.SCHEME, PseudoHeader.PATH),
    transport=TransportParameters(
        max_idle_timeout=30000,
        max_udp_payload_size=1472,
        initial_max_data=15728640,
        initial_max_stream_data_bidi_local=6291456,
        initial_max_stream_data_bidi_remote=6291456,
        initial_max_stream_data_uni=6291456,
        initial_max_streams_bidi=100,
        initial_max_streams_uni=103,
        order=(
            Parameter.MAX_IDLE_TIMEOUT,
            Parameter.MAX_UDP_PAYLOAD_SIZE,
            Parameter.INITIAL_MAX_DATA,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_LOCAL,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_REMOTE,
            Parameter.INITIAL_MAX_STREAM_DATA_UNI,
            Parameter.INITIAL_MAX_STREAMS_BIDI,
            Parameter.INITIAL_MAX_STREAMS_UNI,
            Parameter.INITIAL_SOURCE_CONNECTION_ID,
            Parameter.VERSION_INFORMATION,
            Parameter.MAX_DATAGRAM_FRAME_SIZE,
            Parameter.GOOGLE_CONNECTION_OPTIONS,
            Parameter.INITIAL_ROUND_TRIP_TIME,
        ),
        max_datagram_frame_size=65536,
        google_connection_options=(b"ORIG",),
        grease=True,
        grease_version=True,
        shuffle=True,
    ),
    tls=quic_hello,
    grease=True,
)


async def main() -> None:
    async with Client(versions=("h3",), http3=http3, headers=[("priority", "u=0, i")]) as client:
        _ = await client.get("https://pingly.us.kg/api/all")
        await client.close()  # the next request opens a new connection, which resumes the session
        report = (await client.get("https://pingly.us.kg/api/all")).json()
        print(report["tls"]["ja4"] == JA4.of(quic_hello, JA4Transport.QUIC).text, report["tls"]["ja4"])  # True q13d0313h3_55b375c5d22e_b0954bf1abdf
        print(report["http3"]["h3_text"])  # 1:65536;6:262144;7:100;51:1;GREASE|m,a,s,p


asyncio.run(main())

tls is a ssl2.ClientHello; BoringSSL sends it byte for byte or the client refuses it with the reason. http2 is an Http2Settings with the SETTINGS, WINDOW_UPDATE, priorities and pseudo-header order. http3 is an Http3Settings with the HTTP/3 SETTINGS, pseudo-header order, QUIC transport parameters and QUIC version. Neither has a default: h2 in the ALPN offered over TCP, which is the ClientHello's when tls is given and that of versions otherwise, needs http2, and h3 in versions needs http3. A connection that must be HTTP/1.1, such as the TLS hop to an https proxy or a WebSocket fallback, offers only http/1.1 and drops the ALPS extension.

WebSocket

import asyncio

from boring_http import Client, Http2Settings
from ssl2 import AkamaiFingerprint

http2 = Http2Settings(AkamaiFingerprint.parse("1:65536;2:0;4:6291456;6:262144|15663105|0|m,a,s,p"))


async def main() -> None:
    async with Client(http2=http2) as client:
        websocket = await client.websocket("wss://echo.websocket.org/")
        print((await websocket.receive())[:17])  # Request served by
        await websocket.send("hello")
        print(await websocket.receive())  # hello
        await websocket.send(b"\x00\x01")
        print(await websocket.receive())  # b'\x00\x01'
        await websocket.close()
        print(websocket.close_code)  # 1000


asyncio.run(main())

Over HTTP/1.1 this is the Upgrade handshake. Over HTTP/2 and HTTP/3 it is Extended CONNECT when the server advertises SETTINGS_ENABLE_CONNECT_PROTOCOL, otherwise the client opens an HTTP/1.1 connection for it. subprotocols=[...] offers subprotocols; websocket.subprotocol is the one chosen.

uvloop

import uvloop

from boring_http import Client, Http3Settings, Parameter, Setting, TransportParameters
from ssl2 import PseudoHeader

http3 = Http3Settings(
    settings=((Setting.QPACK_MAX_TABLE_CAPACITY, 65536), (Setting.MAX_FIELD_SECTION_SIZE, 262144), (Setting.QPACK_BLOCKED_STREAMS, 100)),
    pseudo_header_order=(PseudoHeader.METHOD, PseudoHeader.AUTHORITY, PseudoHeader.SCHEME, PseudoHeader.PATH),
    transport=TransportParameters(
        max_idle_timeout=30000,
        max_udp_payload_size=1472,
        initial_max_data=15728640,
        initial_max_stream_data_bidi_local=6291456,
        initial_max_stream_data_bidi_remote=6291456,
        initial_max_stream_data_uni=6291456,
        initial_max_streams_bidi=100,
        initial_max_streams_uni=100,
        order=(
            Parameter.MAX_IDLE_TIMEOUT,
            Parameter.MAX_UDP_PAYLOAD_SIZE,
            Parameter.INITIAL_MAX_DATA,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_LOCAL,
            Parameter.INITIAL_MAX_STREAM_DATA_BIDI_REMOTE,
            Parameter.INITIAL_MAX_STREAM_DATA_UNI,
            Parameter.INITIAL_MAX_STREAMS_BIDI,
            Parameter.INITIAL_MAX_STREAMS_UNI,
            Parameter.INITIAL_SOURCE_CONNECTION_ID,
            Parameter.VERSION_INFORMATION,
        ),
    ),
)


async def main() -> None:
    async with Client(versions=("h3",), http3=http3) as client:
        print((await client.get("https://pingly.us.kg/api/all")).version)  # h3


uvloop.run(main())

Every path, QUIC included, runs unchanged on uvloop.

Performance

Against a Go server (net/http and quic-go) on loopback, so the server is never the limit: 1000 requests for an 86-byte JSON body, sequentially on one connection and with 32 in flight, then one 50 MB download and one 20 MB upload per protocol. The first six rows are requests per second, the rest MB/s, - means the client does not speak that protocol. Python 3.14.8 on Linux, one process per measurement.

HTTP/1.1 and HTTP/2 are Python framing over BoringSSL records; HTTP/3 is a QUIC stack written in Python with BoringSSL doing the cryptography, which is where the gap to libcurl's HTTP/3 comes from. The same code holds 1000 open clients per protocol, 20000 requests with 256 in flight, parallel multi-megabyte transfers and 5% datagram loss on the QUIC path.