Early-Data HTTP Header: Syntax, Directive, Examples

The Early-Data HTTP Header is set by an intermediate to indicate that the request was sent using TLS early data. TLS 1.3 is a significant update to TLS. TLS 1.3 introduces a number of enhancements aimed at enhancing security and performance. Additionally, the Early-Data HTTP Header specifies that the intermediary understands the status code 425 (Too Early). The HTTP 425 Too Early response status code indicates that the server is hesitant to risk executing a request that could be replayed, hence creating the possibility of a replay attack. There is only one value using the Early-Data HTTP Header. The value using the Early-Data HTTP Header is a numeric value. The example of Early-Data HTTP Header is written below. 

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

The Early-Data Request Header can be seen above. In this article, the Early-Data HTT Header Syntax, Directive and Uses examples will be processed. 

What is Early-Data HTTP Header?

An intermediary sets the Early-Data HTTP Header to indicate that the request was transmitted using TLS early data and that the intermediate understands the 425 (Too Early) response code. The Early-Data HTTP Header is not specified by the request’s originator (i.e., a browser).

What is the Syntax of the Early-Data HTTP Header?

The Early-Data HTTP Header has only one value in its syntax. The syntax using the Early-Data HTTP Header is written below. 

Early-Data: 1

What is the DirEarly-Dataive of Early-Data HTTP Header?

The Early-Data HTTP Header does not accept any directives. 

How to use Early-Data HTTP Header?

The Early-Data HTTP Header is a type of HTTP header that enables clients to instantly deliver requests. This is used to ensure that no one or two round-trip delays occur during the execution of the Transport Layer Security (TLS) handshake. When the Early-Data HTTP Header is set, it indicates that the intermediary agent conveyed the request using TLS early data. Additionally, it signifies that the intermediate agent comprehended the status code 425 (Too Early).

Examples of Early-Data HTTP Header Use

The following is an example of how to use the Early-Data HTTP Header. 

GET /resource HTTP/1.0
Host: www.facebook.org
Early-Data: 1
GET /resource HTTP/1.0
Host: www.pinterest.com
Early-Data: 1
GET /resource HTTP/1.0
Host: www.ygentertainment.com
Early-Data: 1

What is the Specification Document for Early-Data HTTP Header?

There is only one specification document for the Early-Data HTTP Header which is the RFC 8470. The RFC 8470 Article 5.1. mentions the Early-Data HTTP Header’s definition. This article also mentioned the Early-Data HTTP Header syntax and examples. 

What are the types of Early-Data HTTP Header?

The Early-Data HTTP Header Types are listed below.

  1. The Early-Data HTTP Header is a Request Header that contains information about the TLS early data and status code. 
  2. The Early-Data HTTP Header is a Response header that may contain additional information about the answer, such as its location or the server that generated it.

What are the similar HTTP Headers to the Early-Data HTTP Header?

There is no available similar HTTP Header to the Early-Data HTTP Header. 

Which Browsers Support Early-Data HTTP Header? 

There are multiple browsers that support Early-Data HTTP Header. The following browsers are listed below.

  • Firefox Browser is compatible with the Early-Data HTTP Header.
  • Firefox for Android Browser is compatible with the Early-Data HTTP Header.

You can see an image that shows cross-browsers compatibility of Early-Data HTTP Headers below.

Early-Data HTTP Header
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