Android reminders not going off? 6 fixes that work
Short answer: most missed reminders on Android come from battery optimization or a missing "Alarms & reminders" permission. Fix those two first, then check notifications and Do Not Disturb.
1. Allow notifications
Settings → Apps → your reminder app → Notifications → Allow. Check that the reminder channel itself isn't turned off.
2. Allow "Alarms & reminders"
On Android 12 and later, apps need this special permission to ring at an exact minute. Without it, a 3:15 reminder may show up at 3:22.
3. Turn off battery optimization for the app
Settings → Apps → the app → Battery → Unrestricted (names vary: "Don't optimize", "No restrictions"). This is the fix for "reminders only appear when I unlock the phone".
4. Check Do Not Disturb and Focus modes
Allow the app as an exception, or use an alarm-style reminder for things that must ring through.
5. Check the notification sound
Reminder sounds use the notification volume, alarm-style ones use the alarm volume. Make sure neither is muted.
6. Restart and reopen once
After a phone update or restart, open the app once so it can re-register its alarms.
A reminder app that helps
Naglet checks these for you: it shows a card to allow exact alarms and battery settings, re-registers reminders after a restart, and keeps re-alerting until you tap Done.
FAQ
Why do reminders only show up when I unlock my phone?
That is almost always battery optimization delaying the app while the screen is off. Set the app to Unrestricted.
Do reminders survive a restart?
Good reminder apps re-register their alarms after a reboot. If yours don't, open the app once after restarting.
Why is my reminder a few minutes late?
Without the exact alarm permission, Android may batch alarms to save battery. Allow Alarms & reminders.