"Styled text to HTML tags" type converter app?

[macstatic]

I'm looking for an app for writing styled text (i.e. bold, italic, underlined etc.) and then output (save, convert or export) that into HTML tags.

I've found tools that do this online such as the "Convert text into HTML" tool at unit-conversion.info and "Word to HTML" which is OK for the occasional conversions, but for a larger project I'd like something that can save my work and let me continue the next day.
Is anything like that available on the Mac platform, or a hidden feature in some common Mac software?

 

[admwright]

What about using a markdown editor? I use Typora (https://typora.io/) on Windows and they now have a beta for OSX. It has options for export to multiple formats, including HTML.