Percent-encoding is a mechanism for representing characters that cannot be used directly in URLs by replacing them with % followed by two hexadecimal digits. It is also known as URL encoding.

For example, a space becomes %20, and the Japanese character "あ" becomes %E3%81%82 in UTF-8. JavaScript provides encodeURIComponent() for encoding and decodeURIComponent() for decoding. Web development fundamentals books cover URL encoding in detail.

RFC 3986 specifies that all characters except unreserved characters (A-Z, a-z, 0-9, -, _, ., ~) must be percent-encoded.

Percent-encoding is automatically applied when sending search queries and form data. When handling Japanese URLs, note that browsers display decoded URLs while the actual URL is encoded. HTTP protocol guides explain URL structure and encoding in detail.