Making text URL-safe
A URL can only contain a limited set of characters, and several of those carry structural meaning. Percent-encoding turns everything else — spaces, ampersands, non-Latin characters — into %XX escapes so a value can sit inside a query string without being mistaken for part of the URL's structure.
Component versus whole URL
The distinction matters. When you encode a single parameter value you want the strict, component-level encoding that also escapes :/?&=. When you are cleaning up an entire address you want those left in place. This tool exposes both so you are never forced to hand-fix the over- or under-encoded result. Everything runs on your device.