International standardBishop, Mike; Akamai. "RFC 9114: HTTP/3". rfc-editor. Retrieved 6 June 2022. (HTTP/3 also uses the completed QUIC protocol described in RFC 9000 and related RFCs such as RFC 9001)
Developed byIETF
IntroducedRFC 9114

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),[1] HTTP/3 uses QUIC, a multiplexed transport protocol built on UDP.[2] On 6 June 2022, IETF published HTTP/3 as a Proposed Standard in RFC 9114.[3]

HTTP/1Transport Layer SecurityTransmission Control ProtocolHTTP/2TLS 1.2Transmission Control ProtocolHTTP/3TLS 1.3QUICUser Datagram ProtocolInternet Protocol
About this image
Protocol Stack of HTTP/3 compared to HTTP/1.1 and HTTP/2

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, for many websites, is the only HTTP version deployed).[4][5] HTTP/3 is supported by 75% of tracked web browser installations (and 81% of "tracked desktop" web browsers),[6] and 26% of the top 10 million websites.[7] It has been supported by Chromium (and derived projects including Google Chrome, Microsoft Edge, Samsung Internet, and Opera)[8] since April 2020 and by Mozilla Firefox since May 2021.[6][9] Safari 14 (on macOS Big Sur and iOS 14, and "is a major new feature in iOS 15";[10] for apps) implemented the protocol but it remains disabled by default.[11]


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.[16] Firefox added support for HTTP/3 in November 2019 through a feature flag[6][17][18] and started enabling it by default in April 2021 in Firefox 88.[6][9] Experimental support for HTTP/3 was added to Safari Technology Preview on April 8, 2020[19] and was included with Safari 14 that ships with iOS 14 and macOS 11,[11][20] but it's still disabled by default as of Safari 16, on both macOS and iOS.[citation needed]

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.[21][22] There is client support for HTTPS resource records since Firefox 92, iOS 14, reported Safari 14 support, and Chromium supports it behind a flag.[23][24][25]




Browser support for HTTP/3
Browser Version implemented (disabled by default) Version shipped (enabled by default) Comment
Chrome Stable build (79) December 2019 87[6] April 2020[26] 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[9] April 2021[27]
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.[28]


Open-source libraries that implement client or server logic for QUIC and HTTP/3 include[29]

Libraries implementing HTTP/3
Name Client Server Programming language Company Repository
lsquic Yes Yes C LiteSpeed
nghttp3 Yes Yes C
h2o No Yes C
libcurl[30][31] Yes No C
MsQuic[32] Yes Yes C Microsoft
proxygen Yes Yes C++ Facebook
Cronet Yes Yes C++ Google
.NET[33] Yes Yes C# (using MsQuic)[34] Microsoft
quic-go Yes Yes Go
http3 Yes Yes Haskell
Kwik Yes Yes Java
Flupke Yes Yes Java
aioquic Yes Yes Python
quiche Yes Yes Rust Cloudflare
neqo Yes Yes Rust Mozilla
quinn Yes Yes Rust
s2n-quic Yes Yes Rust Amazon Web Services


See also


  1. ^ Cerf, V.; Dalal, Y.; Sunshine, C. (December 1974). "Specification of Internet Transmission Control Program". IETF: RFC0675. doi:10.17487/rfc0675.
  2. ^ "What is HTTP/3?". Cloudflare. Archived from the original on 4 July 2022. Retrieved 12 July 2022.
  3. ^ "HTTP/3". 6 June 2022. Retrieved 6 June 2022.
  4. ^ Perna, Gianluca; Trevisan, Martino; Giordano, Danilo; Drago, Idilio (1 April 2022). "A first look at HTTP/3 adoption and performance". Computer Communications. 187: 115–124. doi:10.1016/j.comcom.2022.02.005. ISSN 0140-3664. S2CID 246936473.
  5. ^ "HTTP/3 is Fast". Request Metrics. Retrieved 1 July 2022.
  6. ^ a b c d e ""HTTP/3" | Can I use... Support tables for HTML5, CSS3, etc". Retrieved 2 April 2023.
  7. ^ "Usage of HTTP/3 for websites". World Wide Web Technology Surveys. W3Techs. Retrieved 2 April 2023.
  8. ^ "Enabling QUIC in tip-of-tree". Retrieved 8 April 2021.
  9. ^ a b c Damjanovic, Dragana (16 April 2021). "QUIC and HTTP/3 Support now in Firefox Nightly and Beta". Mozilla Hacks – the Web developer blog. Retrieved 17 April 2021.((cite web)): CS1 maint: url-status (link)
  10. ^ "Apple Developer Documentation". Retrieved 16 February 2023.
  11. ^ a b "Safari 14 Release Notes". Retrieved 4 December 2020.
  12. ^ Shade, Robbie (8 July 2016). HTTP/2 Semantics Using The QUIC Transport Protocol. IETF. I-D draft-shade-quic-http2-mapping.
  13. ^ Cimpanu, Catalin (12 November 2018). "HTTP-over-QUIC to be renamed HTTP/3 | ZDNet". ZDNet. Retrieved 12 November 2018.
  14. ^ Nottingham, Mark (28 October 2018). "Identifying our deliverables". IETF Mail Archive.
  15. ^ "Hypertext Transfer Protocol Charter". Retrieved 2 September 2020.
  16. ^ "Enabling QUIC in tip-of-tree". Retrieved 8 April 2021.
  17. ^ Daniel, Stenberg. "Daniel Stenberg announces HTTP/3 support in Firefox Nightly". Twitter. Retrieved 5 November 2019.
  18. ^ Cimpanu, Catalin (26 September 2019). "Cloudflare, Google Chrome, and Firefox add HTTP/3 support". ZDNet. Retrieved 27 September 2019.
  19. ^ "Release Notes for Safari Technology Preview 104". 8 April 2020. Retrieved 7 August 2020.
  20. ^ Ng, Gary (23 June 2020). "Apple's Safari Adds Support for HTTP3 in iOS 14 and macOS 11". Retrieved 25 June 2021.
  21. ^ "HTTPS RR". MDN. Mozilla. Retrieved 25 October 2022.
  22. ^ Schwartz, Benjamin M.; Bishop, Mike; Nygren, Erik (12 June 2020). Service binding and parameter specification via the DNS. IETF. I-D draft-ietf-dnsop-svcb-https.
  23. ^ "Firefox 92 for developers". Mozilla Corporation. 7 September 2021. Retrieved 25 October 2022.
  24. ^ "Feature: HTTP->HTTPS redirect for HTTPS DNS records". Google Inc. Retrieved 25 October 2022.
  25. ^ Patrick Mevzek (24 August 2021). "What's the use case of SVCB (type 65 , service binding) RR". Stack Exchange Inc. Retrieved 25 October 2022.
  26. ^ "Enabling QUIC in tip-of-tree". Retrieved 9 April 2021.
  27. ^ "Firefox Release Owners - MozillaWiki". Retrieved 9 April 2021.
  28. ^ Jen Simmons (4 April 2023). "HTTP/3 support shipped in Safari 14.0". GitHub. Retrieved 7 April 2023.
  29. ^ "QUIC Implementations". GitHub. Retrieved 8 April 2021.((cite web)): CS1 maint: url-status (link)
  30. ^ "First HTTP/3 with curl". Daniel Stenberg. 5 August 2019. Retrieved 2 October 2019.
  31. ^ "cURL HTTP3 wiki". Daniel Stenberg. 26 September 2019. Retrieved 2 October 2019.
  32. ^ "MsQuic is Open Source". 28 April 2020. Retrieved 28 April 2020.
  33. ^ "HTTP/3 support in .NET 6". 17 September 2021. Retrieved 17 September 2021.
  34. ^ "HTTP/3 support in .NET 6". .NET Blog. 17 September 2021. Retrieved 12 January 2022.
  35. ^ "LiteSpeed Web Server Release Log - LiteSpeed Technologies". Retrieved 12 February 2022. Enable HTTP/3 v1 by default.
  36. ^ "Release 2.6.0 · caddyserver/caddy". Github. 22 September 2022. Retrieved 20 September 2022.
  37. ^ "Introducing a Technology Preview of NGINX Support for QUIC and HTTP/3". NGINX. 10 June 2020. Retrieved 11 June 2020.
  38. ^ "Binary Packages Now Available for the Preview NGINX QUIC+HTTP/3 Implementation". NGINX. 8 February 2023. Retrieved 30 March 2023.
  39. ^ "Experiment with HTTP/3 using NGINX and quiche". The Cloudflare Blog. 17 October 2019. Retrieved 9 November 2019.
  40. ^ Tratcher. "Use ASP.NET Core with HTTP/3 on IIS". Retrieved 29 April 2022.
  41. ^ "Announcing HAProxy 2.6". HAProxy Blog. 31 May 2022.
  42. ^ "QUIC Implementation in HAProxy". HAProxyConf video presentation.