Fill "Your HTML" editor with your HTML source code. You have several possibilities:
Copy and paste your HTML source code
Drag and drop your HTML file
Directly type in the "Your HTML" editor
Click on "export minified HTML" button in order to download minified HTML.
About Hypertext Markup Language (HTML)
Minification is the process of removing all unnecessary characters in order to reduce or compress HTML code, in order to decrease the HTML file size.
HTML minifier is a SEO tools that can help boost your site speed (SEO factor). Decrease the loading time of the web pages improves conversion. The search engines penalize websites that are too long to load.