GlossaryQUIC

QUIC

QUIC is a modern internet transport protocol that sends data over UDP with built-in encryption and faster connection setup than TCP. Originally developed at Google and standardized by the IETF, QUIC carries several independent streams in one connection, so one lost packet does not stall everything else. QUIC is the foundation of HTTP/3.

Why it matters

QUIC makes video start faster and stall less, especially on mobile networks where packet loss and network switches are common. Viewers who wait longer for a first frame are more likely to leave, so faster connections can protect engagement without any change to the video itself.

How it works

  1. QUIC runs on UDP and combines connection setup and encryption into one fast handshake.
  2. Returning clients can often send data immediately, without waiting for a full round trip.
  3. Several independent streams share one connection, so a lost packet only delays its own stream.
  4. Connections can survive a phone switching from Wi-Fi to mobile data without starting over.

QUIC vs TCP: what is the difference?

QUIC runs over UDP and builds in encryption, while TCP needs a separate TLS step on top. QUIC sets up connections faster and avoids head-of-line blocking, where one lost packet holds up everything behind it. TCP is older, universally supported and handled well by every network. QUIC is now widely used by major browsers and CDNs.

Does QUIC improve video streaming?

Yes, mostly through faster startup and fewer stalls on lossy networks. QUIC shortens connection setup and keeps one lost packet from blocking other data. Gains are largest on mobile and congested networks and smaller on stable home broadband. The streaming format does not change; HLS or DASH segments are simply delivered over HTTP/3 on top of QUIC.

Where it's used

OTT services, live sports streamers and short video apps benefit from QUIC when their CDN delivers video over it, giving faster starts and fewer stalls when phones switch networks.

By the numbers

  • QUIC was published by the IETF as RFC 9000, a Proposed Standard titled "QUIC: A UDP-Based Multiplexed and Secure Transport," in May 2021. (RFC 9000, IETF Datatracker)

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