Which is the best online source for learning programming languages for free?

Udemy provides free courses for beginners. Also, Microsoft Virtual Academy is a nice place to learn. Do check their websites.

Tutorial Point Solo and Google Developers are the good options there.

There are a lot of sources available in internet for learning programming languages. Some websites are given below: www.tutorialspoint.com www.codecademy.com www.w3schools.com www.programminglanguages.com And, you can learn languages by youtube in which lots of video lectures available.