Clarify that navigator.userAgentData is not mature

[sideshowbarker]

Fixes #11934

[github-actions]

Preview URLs

• https://pr12017.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Navigator/platform

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/API/Navigator/platform
Title: Navigator.platform
on GitHub

No new external URLs

(this comment was updated 2022-01-15 05:14:23.603775)

[wbamberg]

I thought it was weird to deprecate a feature when the replacement isn't available cross-browser or even standardised! Do you know where it is deprecated? https://html.spec.whatwg.org/multipage/system-state.html#dom-navigator-platform-dev doesn't say anything to that effect.

[sideshowbarker]

I thought it was weird to deprecate a feature when the replacement isn't available cross-browser or even standardised! Do you know where it is deprecated? html.spec.whatwg.org/multipage/system-state.html#dom-navigator-platform-dev doesn't say anything to that effect.

There’s been discussion about this elsewhere, but the gist of it is:

• this is one of key use cases for our proposed “Discouraged” language (vs “Deprecated”) — as discussed in https://github.com/mdn/content/discussions/5549
• developers should not use navigator.platform because it’s not guaranteed to return what they’d expect.

Specifically, the spec allows browsers to simply return the empty string fornavigator.platform. That’s not what developers would expect it to return, and it’s not useful in any way. So we want to warn developers away from trying to use it. That’s also why we have the existing MDN article saying:

The specification allows browsers to always return the empty string, so don't rely on this property to get a reliable answer.

Further, in general most everything in the NavigatorID mixin https://html.spec.whatwg.org/multipage/system-state.html#client-identification is effectively deprecated because:

• At the end of https://html.spec.whatwg.org/multipage/system-state.html#client-identification the spec has a big red note that ends with:

  user agent implementers are strongly urged to include as little information in this API as possible.

• As with navigator.platform, most of the members are defined by the spec either as never returning any useful information at all, or else optionally returning something marginally useful, or nothing at useful at all.

In other words, the spec doesn’t deprecate the features but instead actually normatively defines requirements for them — however, the spec-defined requirements intentionally make the features effectively useless or unreliable to developers.

Hence we want to discourage developers from trying to use the features.

[wbamberg]

Thank you for the clarification @sideshowbarker !