GlossaryProtocolsAdvanced

HTTP/3

HTTP/3 is the newest version of HTTP that runs over the QUIC protocol on UDP instead of TCP. This makes connections faster and more resilient, especially on mobile and unstable networks.

Last updated June 8, 2026

Definition

HTTP/3 is the third major version of HTTP and the first to abandon TCP entirely. It runs on top of QUIC, a transport protocol built on UDP, which bakes encryption and connection management directly into the transport layer.

How HTTP/3 works

QUIC establishes a secure connection in fewer round trips than the TCP plus TLS handshake, and it solves "head-of-line blocking" by keeping streams independent. If one packet is lost, other streams keep flowing. Connections can also migrate between networks (Wi-Fi to cellular) without dropping.

Why it matters for scraping and proxies

  • HTTP/3 traffic over UDP behaves differently from TCP, so some proxies and scraping tools cannot yet handle it.
  • Browsers increasingly negotiate HTTP/3, and its fingerprint is another signal anti-bot vendors inspect.
  • Scrapers that fall back to HTTP/2 or HTTP/1.1 while a browser would use HTTP/3 may stand out.

As adoption grows, supporting HTTP/3 and QUIC is becoming important for both performance and for matching the network behavior of authentic browsers.

Examples

1

Google and YouTube serving content over HTTP/3 by default

2

Mobile browsers seamlessly switching networks without dropping a connection

3

CDNs advertising HTTP/3 via the Alt-Svc header

Common Use Cases

Matching browser behavior by supporting HTTP/3 in scrapers
Improving performance on lossy or mobile networks
Detecting whether a target negotiates HTTP/3 before scraping
Routing QUIC traffic through compatible proxy infrastructure

Frequently Asked Questions

HTTP/3 runs over QUIC on UDP instead of TCP, giving faster handshakes, no head-of-line blocking, and seamless connection migration between networks.
Not all of them. Because HTTP/3 uses UDP-based QUIC, many proxies and scraping libraries still only support TCP-based HTTP/1.1 and HTTP/2.
If your target serves HTTP/3 to real browsers, supporting it helps you blend in; otherwise tools that fall back to older versions may look unusual to anti-bot systems.

Keep Learning

All terms

SOCKS5

SOCKS5 is the latest version of the SOCKS proxy protocol. It routes any kind of network traffic — TCP and UDP — between a client and a server through a proxy, with optional authentication and no awareness of the underlying application.

Read definition

HTTP Proxy

An HTTP proxy is an intermediary server that forwards web (HTTP/HTTPS) requests on your behalf, able to read, cache and filter traffic at the application layer.

Read definition

Browser Fingerprinting

Browser fingerprinting identifies and tracks a device by combining dozens of browser and system attributes — like fonts, canvas rendering and user agent — into a near-unique signature.

Read definition

SSL/TLS

SSL/TLS is the encryption protocol that secures data in transit on the web — the 'S' in HTTPS — protecting it from eavesdropping and tampering.

Read definition
Back to Glossary
HTTP/3 Explained: QUIC, Speed & Scraping | ProxyHorizon | ProxyHorizon