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I'm trying to get the hang of this. I notice that sometimes when I plug the charger the macbook boots automatically, other times it doesn't. I know in desktop macs this is determined by a setting in Energy preferences, but not sure when this is supposed to happen with macbooks. Does it change with the model? It's good to know this for troubleshooting. Any insights would be much appreciated.

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  • Each model has different capabilities, so a Wikipedia list seems more practical than asking lots of people their experience. Is there one model you have in mind or does this need to be vague / survey for your needs?
    – bmike
    Dec 22, 2019 at 21:43

3 Answers 3

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Regardless of of the Mac model, the power settings determine if it will boot upon power failure. If this option isn't set, it won't boot.

enter image description here

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    but macbooks don't have this setting if I'm right? that's what I'm querying about. Aug 21, 2018 at 19:30
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It appears that this feature is controlled by a parameter in the Mac's NVRAM (non-volatile RAM, which contains various parameters used during the startup process). The parameter in question is AutoBoot, which controls whether the MacBook will automatically boot when the lid is opened or power is connected (note that there appears to be no way to separate these settings—if you disable boot-on-power, you also disable boot-on-lid-open). The %00 value for this parameter disables automatic boot, and %03 re-enables it. These values can be changed using the nvram command-line tool.

So, to disable automatic booting when power is connected, run the following command in the Terminal application (found in /Applications/Utilities/Terminal.app) by copy-pasting it into the Terminal, then pressing return. Note that this must be run by an administrator account.

sudo nvram AutoBoot=%00

You'll then see a prompt that looks like this:

Terminal password prompt

Type your password, then press return. Nothing will appear on the screen as you are typing; this is normal.

To revert the changes (i.e., to restore the automatic booting behavior), execute the following command (once again as an administrator):

sudo nvram AutoBoot=%03

After entering your password (if prompted), the setting will be reset to the default.

To view the current values of the data in NVRAM, run the command nvram -p in Terminal. Look for the key on the right-hand side called AutoBoot. If this is set to %03, the laptop will automatically boot after a power failure (i.e., when re-connected to AC power); if AutoBoot set to %00, it won't.

Note that NVRAM values change from time to time, so this may not be applicable in the future. Moreover, if modification of these values causes further issues, you can reset your NVRAM to its factory state by following this process.

Here's an article with more information about the NVRAM parameters on the 2016 MacBook Pro.

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  • with you folks out there there's no more need for teachers, Thanks!. Also, I knew more or less of this autoboot in newer macs, I was interested mostly on 2015 and before mac laptops. By what I could test last week, these will always boot if you plug the magsafe after having disconnected magsafe and battery connector, so there's no need to use the power-on pads on the logic board to start the mac. Aug 29, 2018 at 6:46
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problem solved. My macbook pro early 2011, 13 inches; for two months it was turned off when the magsafe was disconnected, and when connected it was restarted.

Well, it occurred to me to clean the logic card, so I disarmed my macbook and wiped all the dust and lint accumulated for 9 years with a soft and static free-brush while having the logic board properly grounded on a static safe mat / grounded to earth to protect from static buildup.

After this, for two days I was using my macbook always connected to electricity, but then I disconnected it and now it works normally, with the battery charge. It works normal since I cleaned it thoroughly.enter image description here

To summarize, heat buildup can cause this and a deep repair where you remove the logic board and clean out the case can help.

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