Booting from external hard drive

[Habitus]

Is it possible to boot from a external hard drive instead of my internal drive?

 

[Shake 'n' Bake]

Sure.

Hit the power button and quickly hold option on the keyboard. Pick a drive.

 

[NewMacbookPlz]

Is it possible to boot from a external hard drive instead of my internal drive?

Make sure the external drive is GUID Partition table setup, otherwise you cannot boot from it with an Intel mac...