Flask and Django were two big Python web frameworks, and in 2014, the differences between them are not as big as it used to be. Things are changing whenever there are new developments in the framework and new releases. If you want to build a quick prototype and don't have many users, then Flask would be a good choice. If you have a heavy load, then Django would be better. Flask is best used by a small team of developers. It's very clear and simple. Flask has very few components and hence is easy to learn. Django has a lot of components, which can confuse you in the beginning, but Django has tons of modules to help you out. Django has a very active community, which Flask doesn't have.