Sec-Browsing-Topics header
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
Non-standard: This feature is not standardized. We do not recommend using non-standard features in production, as they have limited browser support, and may change or be removed. However, they can be a suitable alternative in specific cases where no standard option exists.
Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
Warning: This feature is currently opposed by two browser vendors. See the Standards positions section for details of opposition.
Note: An Enrollment process is required to use this feature in your applications.
The HTTP Sec-Browsing-Topics request header sends the selected topics for the current user along with the associated request, which are used by an ad tech platform to choose a personalized ad to display.
If the calling site does not have the Topics API included in a successful privacy sandbox enrollment process, attempting to create or modify Sec-Browsing-Topics fails silently, and any existing Sec-Browsing-Topics header is deleted.
See Using the Topics API for more details.
| Header type | Request header |
|---|---|
| Forbidden request header | Yes (Sec- prefix) |
Syntax
Sec-Browsing-Topics: <array-of-observed-topics>
Directives
A JSON object representing an array of up to three objects representing the current user's selected topics for the last three epochs. Each object contains the following properties:
configVersion-
A string identifying the algorithm (other than the model part) used to calculate the topic.
modelVersion-
A string representing the model used to classify a string (such as a web page's hostname) into topic IDs.
taxonomyVersion-
A string representing the taxonomy version used.
topic-
A number representing the ID of the topic, which can be used by the browser to retrieve the topic from the taxonomy (see an example taxonomy of interests).
version-
The
configVersion,modelVersion, andtaxonomyVersion, concatenated with colons (:) between each.
Examples
The exact property values may vary by browser implementation. An example header from Chrome might look as follows:
Sec-Browsing-Topics: [{configVersion: "chrome.1", modelVersion: "1", taxonomyVersion: "1", topic: 43, version: "chrome.1:1:1"}]
Specifications
This feature is not part of an official standard, although it is specified in the Topics API Unofficial Proposal Draft.