QUIC (HTTP/3)
Also known as: QUIC, HTTP/3, HTTP3, QUIC protocol
QUIC is a modern transport protocol, originally developed by Google, that runs over UDP and builds in encryption, faster connection setup, and better handling of lost packets.
HTTP/3, the latest version of the protocol behind web browsing, runs on top of QUIC. While users rarely notice it directly, QUIC makes websites and video load faster, especially on mobile networks, though it also makes some traditional network security inspection harder.
QUIC (HTTP/3), explained at three levels
At home
QUIC is a newer way for your browser to talk to websites. It connects faster and handles bad Wi-Fi or mobile signals better, so pages load more quickly.
At work
QUIC and HTTP/3 improve website and app performance for customers, especially on mobile connections.
At home
Older web connections needed several back-and-forth steps before loading anything. QUIC combines setup and encryption, so it often starts in one round trip. It can also keep a connection alive when your phone switches from Wi-Fi to mobile data.
At work
QUIC runs over UDP, encrypts nearly all of its headers with TLS 1.3, and supports multiple independent streams, so one lost packet doesn't block everything else. Enabling HTTP/3 on a CDN or web server is often a simple setting.
At home
Because QUIC is so heavily encrypted, network filters can see less of what's happening. In my opinion, that's good for privacy, but it frustrates parents and schools using older filtering tools.
At work
Security teams may block UDP port 443 to force fallback to TCP so firewalls can inspect traffic, at a performance cost. Considerations include visibility, DDoS protection for UDP, load balancer support, and monitoring tools that understand QUIC.
Real-world examples
At home
Sophie noticed videos started faster on her phone on the bus, even as her signal switched between cell towers. The app was using QUIC, which kept the connection going smoothly.
At work
Marcus runs web operations for a Canadian e-commerce site. Turning on HTTP/3 at the company's CDN improved page load times for mobile shoppers in rural areas with spotty connections.
How it compares
| feature | QUIC (HTTP/3) | HTTP/2 |
|---|---|---|
| Runs over | UDP | TCP |
| Connection setup | Faster, encryption built in | Separate TCP and TLS steps |
| Lost packets | Affect only one stream | Can stall all streams |
| Network switching | Connection can survive | Connection restarts |
QUIC fixes TCP's delays for the modern, mobile web.
For analysts
For customer-facing websites, enabling HTTP/3 is usually a quick performance win. I'd coordinate with the security team, since some firewalls treat QUIC traffic differently.
History & origin
Google engineer Jim Roskind designed QUIC around 2012, and Google began testing it in Chrome and its own services in 2013. Because it ran over UDP, it could be deployed without waiting for operating systems or network equipment to change. The Internet Engineering Task Force (IETF) formed a working group in 2016 to standardize it, and QUIC was published as RFC 9000 in May 2021. HTTP/3, based on QUIC, was published as RFC 9114 in June 2022. By the mid-2020s, major browsers, content delivery networks, and services such as YouTube and Facebook used QUIC for a large share of traffic. In my view, QUIC shows how a large company can modernize the internet quickly, for better and for worse.