Crash-free users rate
Crash-free users rate is the share of people who used your app in a period without a single crash. 99.5% means 1 in 200 people hit one.
Also called Crash-free users rate, Crash-free sessions, Crash-free rate.
In plain words
99.4% of people used Fern this week without a crash; the 6 who crashed were all on version 2.4.
How Apparent would say it about Fern, an example app in the live demo.
How it's worked out
People who used the app without a crash ÷ people who used the app. It's 100% minus the crash rate.
Good to know
Crash-free sessions is the same idea per visit: the share of sessions that didn't end in a crash. Someone who opens the app ten times and crashes once spoils one session in ten, but they're one person who wasn't crash-free.
Firebase Crashlytics shows both: crash-free users (people who used the app in the period without a crash) and crash-free sessions.
On Android, Google Play turns it around: Android vitals shows the share of daily users who did crash, and flags apps above 1.09% (a crash-free rate under about 98.9%).
On iOS, App Store Connect and Xcode only count crashes from people who share data with developers, so a tool inside the app is the way to see every one.
The number moves with what you count as a user and over how long: a week's rate is usually lower than a day's, because more people have had the chance to crash. Compare like with like, and by version.
Where the number comes from
Your app's SDK (crashes it catches); Firebase Crashlytics; Google Play Console (Android vitals); App Store Connect and Xcode.