URL Encoder / Decoder
Percent-encode and decode URLs and URL parameters, with both encodeURIComponent and encodeURI modes.
What is it
Spaces, Chinese characters and symbols cannot travel safely inside a URL, so they get replaced by a percent sign plus hex bytes: a space becomes %20, 中 becomes %E4%B8%AD. There are two flavors: encodeURIComponent encodes everything that has a special meaning (good for query parameter values), while encodeURI keeps URL structure intact and only encodes really illegal characters (good for a full URL). This tool gives you both.
Notes & fun facts
Ever pasted a WeChat link and ended up with a monster like https://example.com/?from=%E5%88%86%E4%BA%AB? That is percent encoding doing its job. The classic gotcha: people use encodeURIComponent where they needed encodeURI and accidentally escape the slashes, or the other way around and break a parameter value containing an ampersand. This tool shows both side by side so you can spot which one you meant.
Origin & history
Percent-encoding was invented by Tim Berners-Lee and the early URI working group around 1994, when URLs were first defined in RFC 1738. The rules were later refined by RFC 2396 (1998) and RFC 3986 (2005), which is the document browsers still follow today.