Digest HTTP Header: Syntax, Directive, Examples

The Digest HTTP Header contains a digest of the requested resource’s selected representation. Representations are various forms of a specific resource that may be returned in response to a request: for example, the same resource may be formatted in a specific media type such as XML or JSON, localized to a specific written language or geographical region, and/or compressed or otherwise encoded for transmission. As part of a grammar document’s XML declaration on the first line, the XML header specifies the XML version number and, optionally, the character encodings. The JSON object offers methods for processing and converting values to JavaScript Object Notation (JSON). The selected representation is the actual format of a resource that is returned during content negotiation, as indicated by the headers Representation in the response. In HTTP, content negotiation is the mechanism for sending multiple representations of a resource to the same URI in order to assist the user agent in determining the representation that is most appropriate for the user. The digest refers to the entirety of a resource’s representation, not to a single message. It is useful for ensuring that the representation data was not altered during transmission. There are multiple values using the Digest HTTP Header. The values using the Digest HTTP Header are digest-algorithm and digest-value. An example of Digest HTTP Header is written below. 

Digest: sha-512=\vdtholisticseo8nOJRJH6OWUDBPE=, unixsum=69

The Digest HTTP Header Response Header can be seen above. In this article, the Digest HTTP Header Syntax, Directives, and Uses examples will be processed. 

What is Digest HTTP Header?

The Digest HTTP header is a response HTTP header that contains a small value created by a hash function from the entirety of the message. The Digest HTTP header is a response header that contains a hash of the resource that was requested. The Digest HTTP Header is calculated using the complete representation. Multiple digest values are also conceivable for a single resource, as the representation is determined by the Content-Type and Content-Encoding.

What is the Syntax of Digest HTTP Header?

The Digest HTTP Header has multiple values in its syntax. The syntax using the Digest HTTP Header is written below.

Digest: <digest-algorithm>=<digest-value>
Digest: <digest-algorithm>=<digest-value>,<digest-algorithm>=<digest-value>

What are the Directives of Digest HTTP Header?

The Digest HTTP Header has multiple directives. The directives used for the Digest HTTP Header are listed below.

<digest-algorithm>

It includes a list of supported algorithms, such as SHA-256 and SHA-512.

<digest-value>

It contains the outcome of encoding and digesting the resource representation.

An example directive for using the Digest HTTP Header is written below.

Digest: sha-256=X48E9qOokqqrvdts8nOJRJN%OWDPoyWxBf7kbu9DBPE=
Digest: sha-256=X48E9qOokuqrvdts8nOJRJY3OWDUoyWxBf7obu9DBPE=,unixsum=30637

How to use Digest HTTP Header?

The Digest HTTP Header is used to provide a digest of the requested resource’s chosen representation. For example, the same resource could be formatted in XML or JSON, localized to the written language of a given region, and/or encoded for transmission in one of a variety of formats. After content negotiation, the response’s Representation headers reveal the resource’s actual format, which is the representation that was chosen. Not a specific message, but the entire representation of a resource is what the Digest HTTP Header is meant to cover. To ensure that the representation data has not been altered during transmission, it can be employed.

Examples of Digest HTTP Header Use

The following is an example of how to use the DNT HTTP Header.

The sha-256 algorithm and the digest value, for example, are both provided.

Digest: sha-256=nOJRJholisticseoN3OWDUo9DBPE=

For example, the sha-512 method and the digest value are both provided. The UNIX sum algorithm, which can lead to collisions, is also provided as an option.

Digest: sha-512=\vdtholisticseo8nOJRJN3OWDDBPE=, unixsum=69

What is the Specification Document for Digest HTTP Header?

There is only one specification for the Digest HTTP Header which is the Digest Header. The Digest HTTP Header Section 3 mentioned the definition and applications. This section also includes examples and values for the Digest HTTP Header.

What are the types of Digest HTTP Header?

The Digest HTTP Header Types are listed below.

  1. The Digest HTTP Header is a Response Header that provides a digest of the requested resource’s selected representation.
  2. The Digest HTTP Header is a Representation Header containing information about the resource’s body, such as the MIME type or encoding/compression used.

What are the similar HTTP Headers to the Digest HTTP Header?

There are other similar HTTP to the Digest HTTP Header. The examples are listed below. 

  • Want-Digest HTTP Header: The Want-Digest HTTP header is most commonly used in an HTTP request to request that the server provide a digest of the requested resource using the Digest response header. It is similar to the Digest HTTP Header in that it provides a digest.
  • HTTP Range Request: An HTTP range request instructs the server to return only a portion of an HTTP message to the client. Clients that support random access, data tools that know they only need a portion of a large file, and download managers that allow the user to pause and resume the download can all benefit from range requests. The Digest HTTP Header is similar to this HTTP Header in that it is also a representation header type.
  • 206 Partial Content: The HTTP 206 Partial Content success status response code indicates that the request was successful and that the body contains the requested data ranges, as described in the Range header of the request, which is similar to the Digest HTTP Header that selected representation of the requested.

Which Browsers Support Digest HTTP Header?

The compatibility of browsers for the Digest HTTP Header is unknown.

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