iOS Keeps 64 Pending Notifications Per App, and Alarm Apps Spend Them Fast
A third-party iPhone alarm that works for a week or two and then goes quiet has often used up the 64-notification cap. What the cap is and what to do.
In this article6 sections
A third-party alarm that rang every morning for a week or two and then went silent has usually not crashed. It has run out of scheduled notifications.
The likely cause is a per-app cap: iOS holds at most 64 pending local notifications, keeps the 64 that fire soonest, and discards the rest (Apple, UILocalNotification docs). That page describes the older API; developers report the same ceiling with the newer UserNotifications framework.
Why alarm apps spend the 64 so quickly
An alarm that nags is several notifications, not one. Say an app queues the alarm plus N follow-ups per morning, and only reschedules when you open it:
- N = 3 (4 per day): 64 / 4 = 16 days of cover
- N = 5 (6 per day): 10 days
- N = 9 (10 per day): 6 days
Each extra daily alarm shortens these figures in proportion. Once the queue drains, nothing is left to fire.
What developers and users can do
A developer can use one repeating trigger per alarm, which counts as a single item, and top up the queue on every launch and from background refresh. Apple documents no guaranteed frequency for background refresh. On iOS 26 and later, AlarmKit schedules alarms that override silent mode and Focus (Apple, AlarmKit); Apple’s pages do not say whether those alarms count toward the 64.
A user can open the app every day or two, or check whether it has adopted AlarmKit. A missed alarm may also be a Focus filter problem, and Apple gates Critical Alerts by hand.
Frequently asked questions
Can a repeating notification skip a holiday?
Not by itself. Apple’s UIKit documentation counts a repeating notification as one pending item, but it fires every cycle with the same content. Skipping a date or changing a sound means the app has to run and reschedule, which brings back the dependence on you opening it.
How long can a custom alarm sound be on a notification?
Under 30 seconds, in Linear PCM, MA4, uLaw or aLaw, packaged as aiff, wav or caf. Apple’s UNNotificationSound page says a longer file is replaced by the default sound, so a custom 45-second ringtone silently becomes the stock tone.
Does the Critical Alerts entitlement lift the cap?
Apple has not said so. Critical Alerts concerns how a notification is presented, since it can sound through silent mode and Focus, and Apple reviews each entitlement request individually.