URLエンコード/デコード

URLs are only allowed to contain a limited set of characters, so anything outside that set, spaces, accented letters, and reserved symbols like & ? / =, has to be escaped. Percent-encoding replaces each such byte with a percent sign and its two-digit hexadecimal value, so a space becomes %20 and an ampersand becomes %26.

This tool encodes text and URLs to percent-encoded form and decodes them back. It is built on the browser's standard encodeURIComponent and encodeURI functions, so the output matches exactly what your own JavaScript would produce, and it is UTF-8 safe for international text.

Encoding and decoding run entirely in your browser, so nothing you paste is sent to a server, which is reassuring when a URL contains tokens or query parameters you would rather not share.

The scope toggle matters. Component mode (encodeURIComponent) escapes reserved characters like & = ? / and is what you want for a single query-string value or path segment. Full-URL mode (encodeURI) leaves the structural characters intact so a complete URL stays usable.

A common mistake is encoding an entire URL with component mode, which escapes the :// and ? and breaks the link. Another is double-encoding, where an already-encoded string is encoded again and %20 turns into %2520. When in doubt, decode first to see the raw value.

There is also a historical quirk in query strings: form submissions encode a space as a plus sign, while percent-encoding uses %20. Both are seen in the wild, so decoders generally accept either.