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

The Early-Data header is set by an intermediary to indicate that the request has been conveyed in TLS early data, and also indicates that the 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


Early-Data: 1


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


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

Browser compatibility

BCD tables only load in the browser