URL Encoder / Decoder

RFC 3986 percent-encoding and form encoding. Meant for URL parameter values, not whole URLs.

What this tool does

URL encoding (percent-encoding) rewrites characters that cannot appear literally in a URL: a space becomes %20, and non-ASCII text such as Chinese is first split into UTF-8 bytes and then encoded byte by byte, so 中 becomes %E4%B8%AD. Decoding reverses the process. It runs locally, so pasting full URLs with query strings is not a privacy concern.

Typical use cases

Any time you build a share link, landing-page URL, or callback address containing Chinese text or reserved characters, unencoded &, =, or spaces will corrupt the URL structure. When reading analytics or server logs, decoding long runs of %E4%B8%AD is the only way to see what users actually searched for. And a surprising number of HTTP 400 errors come down to one parameter that was never encoded.

Caveats

encodeURIComponent and encodeURI are not interchangeable: the former encodes / : ? & = and is right for parameter values; the latter preserves those structural characters and is right for whole URLs. Using the wrong one either breaks the parameter or double-encodes it. Another classic trap is + in query strings: form-encoding treats it as a space, while a standards-compliant URL treats it as a literal plus — mismatched rules add or lose spaces.