URL エンコード・デコード
The detailed guide below is currently available in English.
Why URLs need escaping
URLs can only carry a small alphabet reliably: letters, digits, and a handful of reserved symbols with structural jobs. A space, an ampersand in a search term, or a plus sign in an email address would be misread as URL syntax, so each risky character is rewritten as a percent sign followed by its hex code. Encoding turns meaning into safe transport; decoding restores it.
Component versus full URL
This tool encodes like a single query-string component: it escapes the reserved characters "& = ? #" as well. That is what you want when building ?name=… values. It is deliberately stricter than escaping a whole address, where those symbols must survive unescaped to keep the URL's own structure intact.
よくある質問
Why did my + signs turn into %2B instead of a space?
There are two space conventions: forms send spaces as +, while strict percent-encoding uses %20. This tool follows the strict standard and therefore escapes a literal + as %2B, so a plus survives the trip as an actual plus.
Which characters stay untouched?
Unreserved characters — A–Z, a–z, digits, hyphen, underscore, period, and tilde — are always safe and never escaped. Everything else becomes a percent sequence.