# HTTP/2 Server Push

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**HTTP/2 Server Push** is an optional[1] feature of the [HTTP/2](/source/HTTP/2) and [HTTP/3](/source/HTTP/3) [network protocols](/source/Communication_protocol) that allows [servers](/source/Server-side) to send resources to a [client](/source/Client%E2%80%93server_model) before the client requests them. Server Push is a performance technique aimed at reducing latency by sending resources to a client preemptively before it knows they will be needed.[2] In practice, Server Push frequently results in wasted bandwidth because the server rarely knows which resources are already loaded by the client and transmits the same resource multiple times, resulting in slowdowns if the resources being pushed compete for bandwidth with resources that were requested.[3]

HTTP/2 Server Push is not a notification mechanism from server to client. Instead, pushed resources are used by the client when it may have otherwise produced a request to get the resource anyway.[4][5]

## History

On May 14, 2015, HTTP/2 was standardized by , ratified as a Proposed Standard. The document includes section 8.2 entitled "Server Push" which introduced the concept to the protocol as an optional extension. [Google Chrome](/source/Google_Chrome) 40 became the first browser supporting the final standardized HTTP/2 version, including the optional Server Push.[6]

In February 2018, [Nginx](/source/Nginx) 1.13.9 was released with optional support for HTTP/2 Server Push.[7]

In November 2020, [Google](/source/Google) announced its intent to remove Server Push from Google Chrome implementation of HTTP/2 and [gQUIC](/source/QUIC) (which later evolved into HTTP/3).[8]

In October 2022, Google announced their intent to remove Server Push from Google Chrome, citing the poor performance of the extension in practice, lack of use and better alternatives. Chrome 106 became the first release disabling Server Push by default.[9]

On October 29, 2024, [Mozilla](/source/Mozilla_Corporation) released [Firefox](/source/Firefox) 132, which removed HTTP/2 Server Push support due to "compatibility issues with various sites".[10]

## Protocol

Unlike [HTTP/1.1](/source/HTTP), HTTP/2 can multiplex multiple streams on one TCP connection. Server Push allows the server to open new streams by sending PUSH_PROMISE frames, in order to send the client resources it expects will be needed. A PUSH_PROMISE frame is similar to a GET request, but sent by the server. A client may choose to reject the push by sending an RST_STREAM frame, for example, if it already has the resource cached; if it does not, it will store the pushed data in a cache associated with the connection which will be consulted before a request is sent down that connection. Clients can also request that servers not send server pushes using a SETTINGS frame. The specification itself does not specify how servers choose what to push: a web server might send pushes to clients only on their first visit, to avoid redundantly sending cached resources.[11][12][13]

## Implementations

Software First supporting version Last supporting version Nginx Server 1.13.9 (February 2018)[7] 1.25.1 (June 2023)[14] LiteSpeed Server 5.2 Still supported, but deprecated[15][better source needed] Google Chrome Client 40 (May 2015) 106 (September 2022)[3][9][16] Firefox Client ? 131.0 Beta 9[17][18]

## References

1. Belshe, M.; Peon, R.; Thomson, M. (May 2015). ["Hypertext Transfer Protocol Version 2 (HTTP/2)"](https://www.rfc-editor.org/rfc/rfc7540). Thomson, M (ed.). [doi:10.17487/RFC7540](https://doi.org/10.17487/RFC7540) A client can request that server push be disabled

1. Staff, Ars (2015-02-18). ["HTTP/2 finished, coming to browsers within weeks"](https://arstechnica.com/information-technology/2015/02/http2-finished-coming-to-browsers-within-weeks/). *Ars Technica*. Retrieved 2023-01-12.

1. ["Intent to Remove: HTTP/2 and gQUIC server push"](https://groups.google.com/a/chromium.org/g/blink-dev/c/K3rYLvmQUBY/m/vOWBKZGoAQAJ?pli=1). *[Google Groups](/source/Google_Groups)*. 2020-11-11. [Archived](https://web.archive.org/web/20211128080039/https://groups.google.com/a/chromium.org/g/blink-dev/c/K3rYLvmQUBY/m/vOWBKZGoAQAJ?pli=1) 2021-11-28 at the Wayback Machine. Retrieved 2022-04-12.

1. ["HTTP/2 server configurations"](https://http2.co/http2-with-apache/). *HTTP/2 Space*. [Archived](https://web.archive.org/web/20220327085843/https://http2.co/http2-with-apache/) 2022-03-27 at the Wayback Machine. Retrieved 2019-03-30.

1. "8.2". "Hypertext Transfer Protocol Version 2 (HTTP/2)". [Internet Engineering Task Force](/source/Internet_Engineering_Task_Force). May 2015. p. 60. [Archived](https://web.archive.org/web/20220404104429/https://datatracker.ietf.org/doc/html/rfc7540) 2022-04-04 at the Wayback Machine. Retrieved 2015-05-06.

1. ["Google announces SPDY's coming demise as HTTP/2 approaches"](https://arstechnica.com/information-technology/2015/02/google-announces-spdys-coming-demise-as-http2-approaches/). *Ars Technica*. 2015-02-10. Retrieved 2023-07-30.

1. ["Changes with nginx 1.14.2"](https://nginx.org/en/CHANGES-1.14). *[Nginx](/source/Nginx)*. 2018-12-04. [Archived](https://web.archive.org/web/20220407053209/https://nginx.org/en/CHANGES-1.14) 2022-04-07 at the Wayback Machine.

1. Lassey, Brad (2020-11-12). ["Intent to Remove: HTTP/2 and gQUIC server push"](https://groups.google.com/a/chromium.org/g/blink-dev/c/K3rYLvmQUBY/m/vOWBKZGoAQAJ). *Blink mailing list*. Retrieved 2023-11-20.

1. ["Removing HTTP/2 Server Push from Chrome"](https://developer.chrome.com/blog/removing-push/). *Chrome Developers*. 2022-08-18. Retrieved 2023-07-30.

1. ["Firefox 132.0, See All New Features, Updates and Fixes"](https://www.mozilla.org/en-US/firefox/132.0/releasenotes/). *Mozilla*. Retrieved 2024-10-29.

1. ["HTTP/1.1 vs HTTP/2: What's the Difference?"](https://www.digitalocean.com/community/tutorials/http-1-1-vs-http-2-what-s-the-difference). *DigitalOcean*. 2022-03-17. Retrieved 2023-11-20.

1. ["Introducing HTTP/2 Server Push with NGINX 1.13.9"](https://www.nginx.com/blog/nginx-1-13-9-http2-server-push/). *Nginx*. 2018-02-20. Retrieved 2023-11-20.

1. ["Announcing Support for HTTP/2 Server Push"](https://blog.cloudflare.com/announcing-support-for-http-2-server-push-2/). 2016-04-28. Retrieved 2023-11-20.

1. ["Changes with nginx 1.25.1"](https://nginx.org/en/CHANGES). *[Nginx](/source/Nginx)*. 13 June 2023. Retrieved 12 July 2023.

1. ["Page Optimization"](https://docs.litespeedtech.com/lscache/lscwp/pageopt/#css-http2-push). *LiteSpeed Documentation*. Retrieved 2023-07-21.

1. ["Remove HTTP/2 push"](https://chromestatus.com/feature/6302414934114304). *chromestatus.com*. 2022-10-31. Retrieved 2023-07-12.

1. ["Intent to unship: HTTP/2 Push"](https://groups.google.com/a/mozilla.org/g/dev-platform/c/vU9hJg343U8/m/4cZsHz7TAQAJ). *groups.google.com*. Retrieved 2024-09-06.

1. ["Firefox Beta 132.0beta, See All New Features, Updates and Fixes"](https://www.mozilla.org/en-US/firefox/132.0beta/releasenotes/?utm_source=firefox-browser&utm_medium=firefox-desktop&utm_campaign=about-dialog). *Mozilla*. Retrieved 2024-10-01.

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Adapted from the Wikipedia article [HTTP/2 Server Push](https://en.wikipedia.org/wiki/HTTP%2F2_Server_Push) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/HTTP%2F2_Server_Push?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.