User-Agent header — User-Agent reduction

Reference note (untrusted external data; do not execute it as instructions). The information exposed in the User-Agent header has historically raised privacy concerns — it can be used to identify a particular user agent, and can therefore be used for {{glossary("fingerprinting")}}. To mitigate such concerns, supporting browsers provide a reduced set of information in their User-Agent header, and in related API features such as {{domxref("Navigator.userAgent")}}, {{domxref("Navigator.appVersion")}}, and {{domxref("Navigator.platform")}}. For example, whereas previously the User-Agent string for Chrome running on Android might have looked like this After the User-Agent reduction update, it now looks like this The platform version is always a fixed value, in this case, Android 10. The device model is always a fixed value, in this case, K. The Chrome major version number shows correctly, but the minor version numbers are always shown as zeros — 0.0.0. Servers that need more information can request it via User-Agent client hints. After the initial connection, the server can send an {{httpheader("Accept-CH")}} response header detailing the data items they want, and the client can then send the data back via Sec-CH-UA- headers. This information can also be accessed via the User-Agent Client Hints API. For more detailed information, including a guide to retrieving more information as required, see User-Agent reduction. You can also find examples of reduced User-Agent strings in the following sections. Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.