Early-Data Header

Table of Content

• Syntax
• Directives
• Examples
• Browser Compatibility
• How to modify Early-Data header

The Early-Data header is a feature of HTTP/2 that augments performance boost by allowing the client to send HTTP requests in the first round trip (0-RTT) to the server, before the secure transport (TLS) handshake is complete. This means data can be sent immediately, reducing the time it takes to establish a secure connection and kickstart data exchange.

Syntax

The syntax for the Early-Data header is quite straightforward:

GET /resource HTTP/1.1
Early-Data: 1Copy

Directives

The Early-Data header primarily uses "1" as its directive to indicate that the client intends to send early data.

Examples

When a client wants to send early data to a server, it simply includes the Early-Data header with the value set to "1" in its request:

GET /index.html HTTP/1.1
Host: www.example.com
Early-Data: 1Copy

Browser Compatibility

As of now, none of the prime web browsers support the Early-Data header.

How to modify Early-Data header

ModHeader is a Google Chrome extension that lets you add or modify HTTP request headers. However, as the Early-Data header is not supported by Google Chrome (and other prime browsers), the extension does not provide the functionality to modify it.