🔗 What Is URL Percent-Encoding?

Why a space or non-ASCII character turns into something like %20 or %EC%95%88.

Ever typed a non-English word into an address bar and found it turned into a string like %ED%95%9C%EA%B8%80 when copied? Here's why.

A URL was originally ASCII-only

The URL standard (RFC 3986) only permits letters, digits, and a handful of symbols to appear literally. A non-ASCII character or a space has to be converted to UTF-8 bytes first, then each byte represented as % followed by two hex digits — percent-encoding.

Reserved characters

Characters like ?, &, =, #, and / carry special meaning in a URL's structure (separating a query string, marking a fragment, and so on), so putting one of them into a value as literal data requires encoding it, or the URL won't parse as intended.

Where this comes up in practice

This is common when passing a search term containing non-English text or a symbol like & as a query parameter to an API, handling a URL with a space in the filename, or decoding an encoded URL from another service back into human-readable form.

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