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Will the alarm still go off if I turn off the phone before?

Example: when I have low battery, I have to go to sleep and wake up at X o'clock, and there is no charger around. Should I turn off the phone?

Note: If it makes any difference my phone is Galaxy S running froyo

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  • 2
    Star this issue if you're interested in Google adding the necessary framework for a hardware alarm: code.google.com/p/android/issues/detail?id=1942 However, due to the open nature of Android, in the end, it is up to manufacturers to include the necessary hardware for powered-off alarm, and it is impossible for Google to force all manufacturers to do so.
    – Lie Ryan
    Dec 30 '10 at 4:54
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    Actually, it works on OnePlus One (forums.oneplus.net/threads/power-off-alarm.300539) The phone will start itself up, to trigger the alarm! (Probably more brands have this, but experienced it on my OPO.)
    – Paul
    Feb 16 '16 at 12:50
  • Cyanogenmod has this feature. Its installed on OnePlus One. You can install it on Galaxy S though. May 12 '16 at 6:36
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No, if the phone is off, it can't do anything. If it's in sleep mode where the screen is off and it's not in use then the alarm will still function as will other types of notifications. I have never tried this specifically on a Galaxy S but I am fairly confident this is a universal rule.

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    I'll confirm this as a Galaxy S owner. When the phone is off, it's actually off. Not a powered-down mode. Dec 30 '10 at 3:19
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    In the motorola razr d3 it's works when the phone is off :) Jan 22 '14 at 20:12
  • In motorola 2nd gen(2014) when the phone is off..no alarm rings..:(
    – Lucky
    Feb 27 '15 at 17:23
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    I'm using Lenovo K5+. Phone power off but the alarm clock automatic power it on.
    – vee
    Aug 13 '16 at 6:39
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    This answer is not correct as a general rule, my galaxy s advance did support this feature on android 4.1.2, and some other phones do as well. It's disappointing that it is not widely implemented though.
    – BramMooij
    Dec 18 '16 at 23:17
12

Unfortunately, it doesn't work when phone is powered off as some have already suggested.

My suggestion: put it into Airplane Mode - this way, the phone almost consumes zero energy (due to not having any network connection and so on), and you have a good chance that the battery will last until the morning where the alarm shall go off!

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  • But I like to have a soft reset of all the phone ram and components and co over night by turning it off. My Lenovo K6 automatically turned on when the alarm time came, why don't the more expensive phones support it...
    – xeruf
    Oct 4 '18 at 4:58
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I have a OnePlus2 and I got a new phone to replace it. I turned the OnePlus2 off and left it unplugged overnight but didn't disable the alarm. It automatically powered on and rung the alarm in the morning twice for me so far.

So, depending on your phone model, this does seem to be a thing these days.

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    Can somebody explain how this works?
    – Athira
    May 30 '19 at 10:06
  • It looks like for OnePlus it’s an added feature: forums.oneplus.com/threads/power-off-alarm.300539 . The closest thing in Android API I can see is RTC_WAKEUP, but that only works when the device is on (the wakeup refers to the device being in sleep mode such as a locked screen). So, the way it probably works on OxygenOS is that the proprietary alarm app stores its state in a file which OxygenOS reads when shutting down and sets a power wake thing in hardware somewhere.
    – binki
    May 30 '19 at 14:43
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No

Tested it. It didn't go off when the phone was off.

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The feature you are talking about is available in mobiles of companies that use their own custom roms like OnePlus, Huwaei (Honor Series) and Xiaomi [ I know about these only because that's all I have tried].

Although you could try using some kind of Automation or Scheduled Power ON and OFF (if your mobile support this feature}.

These two are the only workarounds. (In my knowledge!)

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  • the feature does not only depend on roms. it also requires hardware support. Jul 25 '20 at 10:18

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