Normally, one uses the standard Python module urllib to translate return strings as GET or POST elements from Unicode to UTF-8.
The module is not available for micropython. This small routine translates existing Unicodes according to the HTML URL Encoding Reference and returns a UTF-8 string.
With reference to the ASCII Encoding Reference your browser will encode input, according to the character-set used in your page. The default character-set in HTML5 is UTF-8.
Get formula-entries from browser unicodes (html5) needs a parsing and converting process to a utf-8 string normally this can be done with the urllib-module this is a extrem short form, developed for html-forms
Using the unquote-function with e.g. "a%C3%A4" -> "aü"