HTML Viewer is an amazing tool that is going to help you learn HTML and gain insight into web development. Not only can you view the HTML source code, but you can also import any website from your phone and view the web version of it. 

This app is so simple and intuitive to use. Just select the website you want to view from your phone, select the device you want to view it on (mobile or desktop), and click on the "Start" button. You can even add multiple websites to view on the same device.

You can also export the HTML code of a website to another app or save it to your phone. You can also search through the HTML code of a website to find specific text or links.