erimental 
    13. [ Permissions-Policy: fullscreen ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/fullscreen)
    14. [ Permissions-Policy: gamepad ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/gamepad) Experimental 
    15. [ Permissions-Policy: geolocation ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/geolocation)
    16. [ Permissions-Policy: gyroscope ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/gyroscope) Experimental 
    17. [ Permissions-Policy: hid ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/hid) Experimental 
    18. [ Permissions-Policy: identity-credentials-get ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/identity-credentials-get) Experimental 
    19. [ Permissions-Policy: idle-detection ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/idle-detection) Experimental 
    20. [ Permissions-Policy: local-fonts ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/local-fonts) Experimental 
    21. [ Permissions-Policy: magnetometer ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/magnetometer) Experimental 
    22. [ Permissions-Policy: microphone ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/microphone)
    23. [ Permissions-Policy: midi ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/midi) Experimental 
    24. [ Permissions-Policy: otp-credentials ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/otp-credentials) Experimental 
    25. [ Permissions-Policy: payment ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/payment) Experimental 
    26. [ Permissions-Policy: picture-in-picture ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/picture-in-picture) Experimental 
    27. [ Permissions-Policy: publickey-credentials-create ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/publickey-credentials-create) Experimental 
    28. [ Permissions-Policy: publickey-credentials-get ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/publickey-credentials-get)
    29. [ Permissions-Policy: screen-wake-lock ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/screen-wake-lock)
    30. [ Permissions-Policy: serial ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/serial) Experimental 
    31. [ Permissions-Policy: speaker-selection ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/speaker-selection) Experimental 
    32. [ Permissions-Policy: storage-access ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/storage-access) Experimental 
    33. [ Permissions-Policy: usb ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/usb) Experimental 
    34. [ Permissions-Policy: web-share ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/web-share)
    35. [ Permissions-Policy: window-management ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/window-management) Experimental 
    36. [ Permissions-Policy: xr-spatial-tracking ](/en-US/docs/Web/HTTP/Headers/Permissions-Policy/xr-spatial-tracking) Experimental 

##  In this article

  * Syntax 
  * Specifications 
  * Browser compatibility 
  * See also 

#  Observe-Browsing-Topics

**Experimental:** **This is an[ experimental technology ](/en-
US/docs/MDN/Writing_guidelines/Experimental_deprecated_obsolete#experimental)
**  
Check the  Browser compatibility table  carefully before using this in
production.

**Non-standard:** This feature is non-standard and is not on a standards
track. Do not use it on production sites facing the Web: it will not work for
every user. There may also be large incompatibilities between implementations
and the behavior may change in the future.

**Warning:** This feature is currently opposed by two browser vendors. See the
Standards positions  section below for details of opposition.

The **` Observe-Browsing-Topics ` ** response header is used to mark topics of
interest inferred from a calling site's URL (i.e. the site where the ad tech `
<iframe> ` is embedded) as observed in the response to a request generated by
a [ feature that enables the Topics API ](/en-
US/docs/Web/API/Topics_API/Using#what_api_features_enable_the_topics_api) .