HTTP/3 is the third major version of the

Hypertext Transfer Protocol The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...

used to exchange information on the

World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web ...

, complementing the widely-deployed HTTP/1.1 and

HTTP/2 HTTP/2 (originally named HTTP/2.0) is a major revision of the HTTP network protocol used by the World Wide Web. It was derived from the earlier experimental SPDY protocol, originally developed by Google. HTTP/2 was developed by the HTTP Working ...

. Unlike previous versions which relied on the well-established TCP (published in 1974), HTTP/3 uses

QUIC QUIC (pronounced "quick") is a general-purpose transport layer network protocol initially designed by Jim Roskind at Google, implemented, and deployed in 2012, announced publicly in 2013 as experimentation broadened, and described at an IETF meet ...

, a

multiplexed In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a ...

transport protocol built on UDP. On 6 June 2022, IETF published HTTP/3 as a

Proposed Standard In computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. The ...

in . File:HTTP-1.1 vs. HTTP-2 vs. HTTP-3 Protocol Stack.svg, frame, Protocol Stack of HTTP/3 compared to HTTP/1.1 and HTTP/2 rect 0 44 85 94 HTTP/1 rect 0 95 85 137

Transport Layer Security Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securi ...

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Transmission Control Protocol The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is common ...

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TLS 1.2 Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in securi ...

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rect 251 44 336 74 HTTP/3 rect 255 90 328 121 TLS 1.3 rect 251 125 336 158

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User Datagram Protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) network ...

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Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. ...

HTTP/3 uses similar semantics compared to earlier revisions of the protocol, including the same request methods, status codes, and message fields, but encodes them and maintains session state differently. However, partially due to the protocol's adoption of QUIC, HTTP/3 has lower latency and loads more quickly in real-world usage when compared with previous versions: in some cases over 3× faster than with HTTP/1.1 (which remains the only HTTP version deployed by many websites). HTTP/3 is supported by 75% of web browsers (and 83% of "tracked desktop" web browsers), and 26% of the top 10 million websites. It has been supported by Chromium (and derived projects including Google Chrome,

Microsoft Edge Microsoft Edge is a proprietary, cross-platform web browser created by Microsoft. It was first released in 2015 as part of Windows 10 and Xbox One and later ported to other platforms as a fork of Google's Chromium open-source project: Android ...

Samsung Internet Samsung Internet Browser (or simply Samsung Internet or ''S Browser'') is a mobile web browser for smartphones and tablets developed by Samsung Electronics. It is based on the open-source Chromium project. It comes pre-installed on Samsung Ga ...

, and

Opera Opera is a form of theatre in which music is a fundamental component and dramatic roles are taken by singers. Such a "work" (the literal translation of the Italian word "opera") is typically a collaboration between a composer and a libr ...

) since April 2020 and by Mozilla Firefox since May 2021. Safari 14 (on

macOS Big Sur macOS Big Sur (version 11) is the seventeenth major release of macOS, Apple Inc.'s operating system for Macintosh computers. It was announced at Apple's Worldwide Developers Conference (WWDC) on June 22, 2020, and was released to the publi ...

and

iOS 14 iOS 14 is the fourteenth major release of the iOS mobile operating system developed by Apple Inc. for their iPhone and iPod Touch lines. Announced at the company's Worldwide Developers Conference on June 22, 2020 as the successor to iOS 13 ...

) implemented the protocol but it remains disabled by default.

History

HTTP/3 originates from an

Internet Draft An Internet Draft (I-D) is a document published by the Internet Engineering Task Force (IETF) containing preliminary technical specifications, results of networking-related research, or other technical information. Often, Internet Drafts are int ...

adopted by the QUIC working group. The original proposal was named "HTTP/2 Semantics Using The QUIC Transport Protocol", and later renamed "Hypertext Transfer Protocol (HTTP) over QUIC". On 28 October 2018 in a mailing list discussion, Mark Nottingham, Chair of the

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

HTTP and QUIC Working Groups, proposed renaming HTTP-over-QUIC to HTTP/3, to "clearly identify it as another binding of HTTP semantics to the wire protocol ..so people understand its separation from QUIC". Nottingham's proposal was accepted by fellow IETF members a few days later. The HTTP working group was chartered to assist the QUIC working group during the design of HTTP/3, then assume responsibility for maintenance after publication. Support for HTTP/3 was added to Chrome (Canary build) in September 2019 and then eventually reached stable builds, but was disabled by a feature flag. It was enabled by default in April 2020. Firefox added support for HTTP/3 in November 2019 through a feature flag and started enabling it by default in April 2021 in Firefox 88. Experimental support for HTTP/3 was added to Safari Technology Preview on April 8, 2020 and was included with Safari 14 that ships with

and

macOS 11 macOS Big Sur (version 11) is the seventeenth major release of macOS, Apple Inc.'s operating system for Macintosh computers. It was announced at Apple's Worldwide Developers Conference (WWDC) on June 22, 2020, and was released to the public ...

, but it's still disabled by default as of Safari 16, on both macOS and iOS.

Comparison with HTTP/1.1 and HTTP/2

HTTP semantics are consistent across versions: the same request methods, status codes, and message fields are typically applicable to all versions. The differences are in the mapping of these semantics to underlying transports. Both HTTP/1.1 and

use TCP as their transport. HTTP/3 uses

, a

transport layer In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end ...

network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...

which uses

user space A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour. Kernel ...

congestion control Network congestion in data networking and queueing theory is the reduced quality of service that occurs when a network node or link is carrying more data than it can handle. Typical effects include queueing delay, packet loss or the blocking of ...

over the

(UDP). The switch to QUIC aims to fix a major problem of HTTP/2 called "

head-of-line blocking Head-of-line blocking (HOL blocking) in computer networking is a performance-limiting phenomenon that occurs when a line of packets is held up in a queue by a first packet. Examples include input buffered network switches, out-of-order delivery a ...

": because the parallel nature of HTTP/2's multiplexing is not visible to TCP's loss recovery mechanisms, a lost or reordered

packet Packet may refer to: * A small container or pouch ** Packet (container), a small single use container ** Cigarette packet ** Sugar packet * Network packet, a formatted unit of data carried by a packet-mode computer network * Packet radio, a fo ...

causes all active transactions to experience a stall regardless of whether that transaction was impacted by the lost packet. Because QUIC provides native multiplexing, lost packets only impact the streams where data has been lost. Proposed DNS resource records SVCB (service binding) and HTTPS would allow connecting without first receiving the Alt-Svc header via previous HTTP versions, therefore removing the 1 RTT of handshaking of TCP. There is client support for HTTPS resource records since Firefox 92, iOS 14, reported Safari 14 support, and Chromium supports it behind a flag.

Implementations

Client

Browser

Libraries

Open-source

libraries A library is a collection of Document, materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or electronic media, digital access (soft copies) materials, and may be a ...

that implement client or server logic for QUIC and HTTP/3 include

Server

* On 7 June 2021, LiteSpeed Web Server (and OpenLiteSpeed) 6.0.2 was released and became the first version to enable HTTP/3 by default. * Caddy web server v2.6.0 (released 20 September 2022) has HTTP/3 enabled by default. *

Nginx Nginx (pronounced "engine x" ) is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache. The software was created by Igor Sysoev and publicly released in 2004. Nginx is free and open-source software ...

support for HTTP/3 is being worked on. A technology preview of nginx with HTTP/3 support was released in June 2020. * Cloudflare distributes a patch for nginx that integrates the quiche HTTP/3 library into it. *

Microsoft IIS Internet Information Services (IIS-pronounced 2S, formerly Internet Information Server) is an extensible web server software created by Microsoft for use with the Windows NT family. IIS supports HTTP, HTTP/2, HTTPS, FTP, FTPS, SMTP and NNTP. ...

support for HTTP/3 is enabled natively with Windows Server 2022/Windows 11.

References

External links

* *
RFC 9114 "Hypertext Transfer Protocol Version 3 (HTTP/3)"

HTTP/3 explained
(

Daniel Stenberg Magnus Daniel Stenberg is a Swedish developer, recipient of the Polhem Prize 2017 for his work on cURL. He was born and raised in Huddinge, a suburb south of Sweden's capital Stockholm. He created a utility which, after various name and licens ...

)
HTTP/3 on caniuse.com

List of QUIC implementations on the IETF QUIC Working Group Wiki

Tool to check if a website supports HTTP/3
{{DEFAULTSORT:HTTP 3 Hypertext Transfer Protocol Application layer protocols Computer-related introductions in 2018