This is a simple and user-friendly extension to use HTML content inside emails. Just simply select the HTML and it will be pasted inside your email, and a preview will be generated, so you can make sure everything works as expected.

You will not see any change in your email when using this extension, except for the first time. The HTML is automatically pasted inside the email and a preview is generated. So, you will only have to check that if you are not sure about the result.

To use this extension, first install the extension and then refresh the tabs of your Gmail account. Once that is done, you can select the "Use in HTML" option from the context menu and start using it.