I see it is possible to open the Watch app from Safari or Chrome using itms-watchs://
or watchface://.
I would like to be able to deep link to (open) a specific watch face from the browser. I see this is possible from other apps like Facer, because if you tap a watch face in that app and then tap the watch button, you will see this:
https://imgur.com/jLDnbBl
I would guess the Facer app is using a URL scheme like watchface://,
so I just need to know how I can do the same thing. I tried something like watchface://https://mysite/mywatchfaceimage.png
but it does not work ("Safari cannot open the page because the address is invalid.").
Turns out deeplinking was not the solution. I found this video: https://developer.apple.com/videos/play/wwdc2020/10100/, which proves (skip to 12:44) that it is possible to link to a watch face from a website, but it requires a .watchface
file, which apparently can only be exported (created) from the Watch app. It is possible to create a watch face from 1 photo in the Photos app by sharing the photo and selecting the Create Watch Face option. However, the catch is, you can't export that watch face until you have added it, which requires you to pair an Apple Watch to your phone first. I didn't have an Apple Watch paired, and so it seemed impossible to create.
Once you add the watch face, in My Faces, select (may have to longpress?) the photo you created as a watch face (there will be two options, one with date/time on top and one on bottom). Then you should see a Share Watch Face option - that is how the .watchface
file gets created.
Apple should provide an export option without requiring you to add the photo watch face, as you do this for other default watch faces anyway...