The best way of how to learn guitar online is using video lessons.
It's the closest thing you'll get to a private tutor but it won't cost the earth.
In fact, it doesn't have to cost anything.
A private tutor can physically see what you are getting right and won't dwell in these areas and can focus on problems, some that you might be aware of.
The problem with video lessons is that you don't have the interaction that you need in order to iron out any bad habits.
You can kind of do a spot check at any time when you are trying to learn the guitar.
When progressing through the chords and wondering whether they sound just right, instead of strumming the chord, play each string individually that is meant to be part of the chord and check you're not muting anything with the edges of your fingers.
The clarity when you are strumming your chords is a big part of sounding like a competent guitarist and it is a really useful exercise to train yourself to make sure each note in the chord sounds clean.
Spend a few moments practicing new chords and play the notes individually with your hand in the correct chord position.
I often see people generally getting the chord shape correct and thinking this is ok, but train your ears to listen out for the full sounding chord.
It might take a bit to get into it, but it is the small things like this in the earlier stages which will make it much easier to learn quickly later on.
When you learn electric guitar online, remember that you need to be your own judge, as you don't have a tutor breathing down your neck, so if you try and be a little disciplined to do this, it will save time learning and you will become better much quicker.