![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUmJkDhudn4AKpoV5bzATEh4u2tsBlProuuhDUymGh5R961j_jqpBcedciUtGH5QqdgJL5A93LEgMx02-DbtmPXvRBJwq0e8bFV28hX7zhYTgdNMH_EUd0eTllrTTZ8zZAK2DoQg/s320/IMG_0057.png)
I’ve already shipped an app that is accessing Face ID on iPhone X, but while testing an unrelated feature the other day, I saw the alert on the left. I thought I had read everything that I needed to about Face ID implementation, but this had slipped past me.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWxFVvPUmts_8Sb8MsTMu5RnS0p3ljQuGMPIus_59RlfbnRtdHSvLxULu9K57fMaRQ9wjEjqseJ0_AC4PTgO4b8bh2KYU5voAqcQVeuBrOCULBoW1V3JsBuuKArHB-pfhyphenhyphentk3OaA/s320/LAContext.png)
I parked it for a while, but I happened to open the
docs on LAContext on an unrelated issue when I saw the
Important information on the right.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjvYJBzzwZ7JFASoKUPWN4p88HdQQjoAfhIcLLcutml-T3_5PvOUdBkiHobkCURM0d_SmR2CtUNbpUAu7dGTsMy4pgLw8197iXMgIs3UMTCPUlv6GOb-h7TjqEVQoaT_facCHFVwQ/s320/NSFaceIDUsageDescription.png)
When you click on
NSFaceIDUsageDescription you see the description on the left. I didn't experience any forced app quitting behavior on device or simulator, but your experience may vary.
With
NSFaceIDUsageDescription added to Info.plist, and a key of “Secure Account Access” like in the right screenshot, users will see a prompt like the one on the right when the app tries to access Face ID the first time.
Glad I caught this in the “one to fix all the iPhone X issues” release of the app I’m working on.