Phased release

Phased release is Apple's option to deliver an approved update to a growing share of your existing users over seven days rather than to everyone at once.

The schedule runs day by day at roughly 1%, 2%, 5%, 10%, 20%, 50%, then 100% of eligible users, and you turn it on per version before submission or before release.

Read "eligible" carefully, because this is where the safety net has a hole. Phased release only governs automatic updates. Anyone who opens the App Store and taps Update gets the new version immediately, whatever percentage you are on. So does anyone following a link to your product page. Your 1% day is 1% of the passive population plus everyone who went looking.

It also does not apply to a brand new app. There is no first release to phase, only updates.

You can pause a phased release at any point from App Store Connect, and pausing stops further distribution while leaving installed users where they are. You can also release to all users immediately, ending the phase early. What you cannot do is pull the version back from people who already have it. The only route out of a bad release is a new version forward.

Pause plus a fast follow-up build is the actual playbook.

See also: staged rollout, App Store version, build.