What is the difference between “Component” and “Full URL”?
Component encodes everything except letters, digits and - _ . ! ~ * ' ( ), which is right for a single query parameter value or path segment. Full URL keeps characters that give a URL its structure, like : / ? & = and #, so you can encode a whole address without breaking it.
Why do spaces sometimes appear as + signs?
HTML forms encode spaces as + in query strings. When decoding, turn on “Treat + as space” for form data. Leave it off for other URLs, where + is a real plus sign.
What if my text has a % sign that isn't a code?
It's left as it is and the rest is still decoded. “100%25 sure and 50% off” becomes “100% sure and 50% off”, and the status line says how many % signs weren't followed by a valid code.
Is URL encoding the same as percent encoding?
Yes. Each unsafe character is replaced by % followed by its byte value in hexadecimal, using UTF-8 for non-English characters. For example, a space becomes %20 and é becomes %C3%A9.