How URL Encoding Works and When You Need It

URLs can only contain a limited set of characters defined by RFC 3986. When a URL contains special characters such as spaces, ampersands, or non-ASCII characters, they must be percent-encoded.

Percent encoding replaces each unsafe character with a % followed by its two-digit hexadecimal ASCII code. A space becomes %20, an ampersand becomes %26. In practice: always encode user-supplied input that appears in query parameters, use encodeURIComponent() in JavaScript (not encodeURI()).