URLs can only contain a limited set of characters. Spaces and other special characters must be percent-encoded. %20 is the UTF-8 byte for a space character in hexadecimal. In query strings, + is also used for spaces.

Double-encoding happens when a URL is encoded twice — so % becomes %25, turning %20 into %2520. This tool decodes one level at a time. If your result still looks encoded, try pasting it in again.

It means the input contains an invalid percent-escape (like %GG or a truncated %2). The tool will try to decode as much as possible and flag the error.

Yes. Paste the full URL and the entire string will be decoded. Individual parameter values will become readable text.