HTTP headers | DNT

Last Updated : 11 May, 2020

The HTTP DNT Header is a request header that allows users to choose if their activity could be tracked by each server and web application that they communicate with via HTTP. The generated header field is a mechanism that allows the user to opt-in or out of the tracking. Tracking allows user to experience personalized content on web. The option to opt-out of tracking was created with growing privacy demands among users.

The tracking preference can only be set if a user has enabled it. A user agent is not allowed to display a tracking preference expression if not enabled tracking preference is set by the user.

Syntax:

DNT:0
DNT:1

Directives :

The following field value is generated for HTTP DNT header field if the tracking preference is set as enabled

1: This directive indicates that user prohibits tracking at the target site.
0: This directive indicates that user allows tracking on or the user has granted an exception at the given target site.

Note : A DNT Header Field can have zero or more extensions. The extensions are determined by the user agent. A DNT header field can be inserted without a field value if the extension is defined but the tracking preference is not set.

Examples:

This is a example from W3C(World Wide Web Consortium) of a DNT header set to field value – 1:
```
GET /something/here HTTP/1.1
Host: example.com
DNT: 1
```
The value of DNT header field can be checked using JavaScript’s navigator.doNotTrack property.
```
console.log(navigator.doNotTrack); 
// prints "1" if DNT is enabled; "0" 
// if the user opted-in for tracking;
// prints "null" if unspecified
```
1. Safari 7.1.3+ , Edge , IE11 and subsequent versions use window.doNotTrack rather than navigator.doNotTrack
2. Prior to Firefox 32, navigator.doNotTrack would report values of yes and no rather than 1 and 0.

Supported Browsers: The browsers supported by HTTP DNT Header are listed below