HTTP/3

HTTP/3 is the third major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web, complementing the widely deployed HTTP/1.1 and HTTP/2. Unlike previous versions which relied on the well-established TCP (published in 1974),^[2] HTTP/3 uses QUIC (officially introduced in 2021),^[3] a multiplexed transport protocol built on UDP.^[4]

HTTP/3

International standard	RFC 9114[1] (HTTP/3 also uses the completed QUIC protocol described in RFC 9000 and related RFCs such as RFC 9001)
Developed by	IETF
Introduced	June 2022
Website	https://httpwg.org/specs/rfc9114.html

Internet history timeline

Early research and development: 1960–1964: RAND networking concepts developed 1962–1964: ARPA networking ideas 1965 (1965): NPL network concepts conceived 1966 (1966): Merit Network founded 1967 (1967): ARPANET planning begins 1967 (1967): Symposium on Operating Systems Principles 1969 (1969): NPL followed by the ARPANET carry their first packets 1970 (1970): Network Information Center (NIC) 1971 (1971): Tymnet switched-circuit network 1972 (1972): Merit Network's packet-switched network operational 1972 (1972): Internet Assigned Numbers Authority (IANA) established 1973 (1973): CYCLADES network demonstrated 1973 (1973): PARC Universal Packet development begins 1974 (1974): Transmission Control Program specification published 1975 (1975): Telenet commercial packet-switched network 1976 (1976): X.25 protocol approved and deployed on public data networks 1978 (1978): Minitel introduced 1979 (1979): Internet Activities Board (IAB) 1980 (1980): USENET news using UUCP 1980 (1980): Ethernet standard introduced 1981 (1981): BITNET established Merging the networks and creating the Internet: 1981 (1981): Computer Science Network (CSNET) 1982 (1982): TCP/IP protocol suite formalized 1982 (1982): Simple Mail Transfer Protocol (SMTP) 1983 (1983): Domain Name System (DNS) 1983 (1983): MILNET split off from ARPANET 1984 (1984): OSI Reference Model released 1985 (1985): First .COM domain name registered 1986 (1986): NSFNET with 56 kbit/s links 1986 (1986): Internet Engineering Task Force (IETF) 1987 (1987): UUNET founded 1988 (1988): NSFNET upgraded to 1.5 Mbit/s (T1) 1988 (1988): Morris worm 1988 (1988): Complete Internet protocol suite 1989 (1989): Border Gateway Protocol (BGP) 1989 (1989): PSINet founded, allows commercial traffic 1989 (1989): Federal Internet Exchanges (FIX East|FIXes) 1990 (1990): GOSIP (without TCP/IP) 1990 (1990): ARPANET decommissioned 1990 (1990): Advanced Network and Services (ANS) 1990 (1990): UUNET/Alternet allows commercial traffic 1990 (1990): Archie search engine 1991 (1991): Wide area information server (WAIS) 1991 (1991): Gopher 1991 (1991): Commercial Internet eXchange (CIX) 1991 (1991): ANS CO+RE allows commercial traffic 1991 (1991): World Wide Web (WWW) 1992 (1992): NSFNET upgraded to 45 Mbit/s (T3) 1992 (1992): Internet Society (ISOC) established 1993 (1993): Classless Inter-Domain Routing (CIDR) 1993 (1993): InterNIC established 1993 (1993): AOL added USENET access 1993 (1993): Mosaic web browser released 1994 (1994): Full text web search engines 1994 (1994): North American Network Operators' Group (NANOG) established Commercialization, privatization, broader access leads to the modern Internet: 1995 (1995): New Internet architecture with commercial ISPs connected at NAPs 1995 (1995): NSFNET decommissioned 1995 (1995): GOSIP updated to allow TCP/IP 1995 (1995): very high-speed Backbone Network Service (vBNS) 1995 (1995): IPv6 proposed 1996 (1996): AOL changes pricing model from hourly to monthly 1998 (1998): Internet Corporation for Assigned Names and Numbers (ICANN) 1999 (1999): IEEE 802.11b wireless networking 1999 (1999): Internet2/Abilene Network 1999 (1999): vBNS+ allows broader access 2000 (2000): Dot-com bubble bursts 2001 (2001): New top-level domain names activated 2001 (2001): Code Red I, Code Red II, and Nimda worms 2003 (2003): UN World Summit on the Information Society (WSIS) phase I 2003 (2003): National LambdaRail founded 2004 (2004): UN Working Group on Internet Governance (WGIG) 2005 (2005): UN WSIS phase II 2006 (2006): First meeting of the Internet Governance Forum 2010 (2010): First internationalized country code top-level domains registered 2012 (2012): ICANN begins accepting applications for new generic top-level domain names 2013 (2013): Montevideo Statement on the Future of Internet Cooperation 2014 (2014): NetMundial international Internet governance proposal 2016 (2016): ICANN contract with U.S. Dept. of Commerce ends, IANA oversight passes to the global Internet community on October 1st Examples of Internet services: 1989 (1989): AOL dial-up service provider, email, instant messaging, and web browser 1990 (1990): IMDb Internet movie database 1994 (1994): Yahoo! web directory 1995 (1995): Amazon online retailer 1995 (1995): eBay online auction and shopping 1995 (1995): Craigslist classified advertisements 1995 (1995): AltaVista search engine 1996 (1996): Outlook (formerly Hotmail) free web-based e-mail 1996 (1996): RankDex search engine 1997 (1997): Google Search 1997 (1997): Babel Fish automatic translation 1998 (1998): Yahoo Groups (formerly Yahoo! Clubs) 1998 (1998): PayPal Internet payment system 1998 (1998): Rotten Tomatoes review aggregator 1999 (1999): 2ch Anonymous textboard 1999 (1999): i-mode mobile internet service 1999 (1999): Napster peer-to-peer file sharing 2000 (2000): Baidu search engine 2001 (2001): 2chan Anonymous imageboard 2001 (2001): BitTorrent peer-to-peer file sharing 2001 (2001): Wikipedia, the free encyclopedia 2003 (2003): LinkedIn business networking 2003 (2003): Myspace social networking site 2003 (2003): Skype Internet voice calls 2003 (2003): iTunes Store 2003 (2003): 4chan Anonymous imageboard 2003 (2003): The Pirate Bay, torrent file host 2004 (2004): Facebook social networking site 2004 (2004): Podcast media file series 2004 (2004): Flickr image hosting 2005 (2005): YouTube video sharing 2005 (2005): Reddit link voting 2005 (2005): Google Earth virtual globe 2006 (2006): Twitter microblogging 2007 (2007): WikiLeaks anonymous news and information leaks 2007 (2007): Google Street View 2007 (2007): Kindle, e-reader and virtual bookshop 2008 (2008): Amazon Elastic Compute Cloud (EC2) 2008 (2008): Dropbox cloud-based file hosting 2008 (2008): Encyclopedia of Life, a collaborative encyclopedia intended to document all living species 2008 (2008): Spotify, a DRM-based music streaming service 2009 (2009): Bing search engine 2009 (2009): Google Docs, Web-based word processor, spreadsheet, presentation, form, and data storage service 2009 (2009): Kickstarter, a threshold pledge system 2009 (2009): Bitcoin, a digital currency 2010 (2010): Instagram, photo sharing and social networking 2011 (2011): Google+, social networking 2011 (2011): Snapchat, photo sharing 2012 (2012): Coursera, massive open online courses 2016 (2016): TikTok, video sharing and social networking

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 four times as fast than with HTTP/1.1 (which, for many websites, is the only HTTP version deployed).^[5][6]

As of September 2024, HTTP/3 is supported by more than 95% of major web browsers in use^[7] and 34% of the top 10 million websites.^[8] It has been supported by Chromium (and derived projects including Google Chrome, Microsoft Edge, Samsung Internet, and Opera)^[9] since April 2020 and by Mozilla Firefox since May 2021.^[7][10] Safari 14 implemented the protocol but it remains disabled by default.^[11]

History

Protocol stack of HTTP/3 compared to HTTP/1.1 and HTTP/2

HTTP/3 originates from an Internet Draft adopted by the QUIC working group. The original proposal was named "HTTP/2 Semantics Using The QUIC Transport Protocol",^[12] and later renamed "Hypertext Transfer Protocol (HTTP) over QUIC".^[13]

On 28 October 2018 in a mailing list discussion, Mark Nottingham, Chair of the IETF 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".^[14] 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.^[15]

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.^[9] Firefox added support for HTTP/3 in November 2019 through a feature flag^[7][16][17] and started enabling it by default in April 2021 in Firefox 88.^[7][10] Experimental support for HTTP/3 was added to Safari Technology Preview on April 8, 2020^[18] and was included with Safari 14 that ships with iOS 14 and macOS 11,^[11][19] but it's still disabled by default as of Safari 16, on both macOS and iOS.^{[citation needed]}

On 6 June 2022, IETF published HTTP/3 as a Proposed Standard in RFC 9114.^[1]

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 HTTP/2 use TCP as their transport. HTTP/3 uses QUIC, a transport layer network protocol which uses user space congestion control over the User Datagram Protocol (UDP). The switch to QUIC aims to fix a major problem of HTTP/2 called "head-of-line blocking": because the parallel nature of HTTP/2's multiplexing is not visible to TCP's loss recovery mechanisms, a lost or reordered packet 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.^[20][21] There is client support for HTTPS resource records since Firefox 92, iOS 14, reported Safari 14 support, and Chromium supports it behind a flag.^[22][23][24]

Implementations

Client

Browser support for HTTP/3

Browser	Version implemented (disabled by default)		Version shipped (enabled by default)		Comment
Chrome	Stable build (79)	December 2019	87[7]	April 2020[25]	Earlier versions implemented other drafts of QUIC
Edge	Stable build (79)	December 2019	87	April 2020	Edge 79 was the first version based on Chromium
Firefox	Stable build (72.0.1)	January 2020	88[10]	April 2021[26]
Safari	Stable build (14.0)	September 2020	16.4	March 2023	Apple is testing HTTP/3 support on some Safari users starting with Safari 16.4.[27]

Libraries

Open-source libraries that implement client or server logic for QUIC and HTTP/3 include^[28]

Libraries implementing HTTP/3

Name	Client	Server	Programming language	Company	Repository
lsquic	Yes	Yes	C	LiteSpeed	https://github.com/litespeedtech/lsquic
nghttp3	Yes	Yes	C		https://github.com/ngtcp2/nghttp3
h2o	No	Yes	C		https://github.com/h2o/h2o
libcurl[29][30]	Yes	No	C		https://github.com/curl/curl
MsQuic[31]	Yes	Yes	C	Microsoft	https://github.com/microsoft/msquic
proxygen	Yes	Yes	C++	Facebook	https://github.com/facebook/proxygen#quic-and-http3
Cronet	Yes	Yes	C++	Google	https://github.com/chromium/chromium/tree/main/net/quic
.NET[32]	Yes	Yes	C# (using MsQuic)[33]	Microsoft	https://github.com/dotnet
quic-go	Yes	Yes	Go		https://github.com/quic-go/quic-go
http3	Yes	Yes	Haskell		https://github.com/kazu-yamamoto/http3
Kwik	Yes	Yes	Java		https://github.com/ptrd/kwik
Flupke	Yes	Yes	Java		https://bitbucket.org/pjtr/flupke
aioquic	Yes	Yes	Python		https://github.com/aiortc/aioquic
quiche	Yes	Yes	Rust	Cloudflare	https://github.com/cloudflare/quiche
neqo	Yes	Yes	Rust	Mozilla	https://github.com/mozilla/neqo
quinn	Yes	Yes	Rust		https://github.com/quinn-rs/quinn
s2n-quic	Yes	Yes	Rust	Amazon Web Services	https://github.com/aws/s2n-quic

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.^[34]
• Caddy web server v2.6.0 (released 20 September 2022) has HTTP/3 enabled by default.^[35]
• Nginx supports HTTP/3 since 1.25.0 (released 23 May 2023). A technology preview of nginx with HTTP/3 support was released in June 2020.^[36] Binary packages of nginx with HTTP/3 support have been released in February 2023.^[37]
• Cloudflare distributes a patch for nginx that integrates the quiche HTTP/3 library into it.^[38]
• Microsoft IIS support for HTTP/3 is enabled natively with Windows Server 2022/Windows 11.^[39]
• HAProxy supports HTTP/3 over QUIC since version 2.6 released on 31 May 2022.^[40][41]
• Nimble Streamer supports HTTP/3 since 4.1.8-1^[42] for HTTP-based protocols.

See also

• Internet portal

• Fast and Secure Protocol – Terminal command scheme used to transfer data