This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The Early-Data header is set by an intermediate to indicates that the request has been conveyed in TLS early data, and additionally indicates that an intermediary understands the 425 (Too Early) status code.  The Early-Data header is not set by the originator of the request (i.e., a browser).

Header type Request header
Forbidden header name no

Syntax

Early-Data: 1

Examples

GET /resource HTTP/1.0
Host: example.com
Early-Data: 1

Specifications

Specification Title
RFC 8470, section 5.1: The Early-Data Header Field Using Early Data in HTTP

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Basic support
Experimental
Chrome ? Edge ? Firefox Full support 58IE No support NoOpera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 58Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.

Document Tags and Contributors

Contributors to this page: m_t, chrisdavidmills, mfuji09
Last updated by: m_t,