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Query parameters that contain spaces, ampersands, or non-ASCII characters must be percent-encoded before being appended to a URL, or the URL will be misinterpreted — an unencoded & inside a value will be read as the start of a new parameter, for instance. This tool handles both directions so you can debug what a captured URL actually decodes to.
Frequently asked questions
What is percent-encoding?
It replaces characters not allowed or with special meaning in a URL, like spaces or ampersands, with a percent sign followed by their two-digit hex code — %20 for a space, for example.
Why is a space sometimes shown as + instead of %20?
The + form is specific to application/x-www-form-urlencoded data from HTML forms and query strings, not the general URL encoding standard, which uses %20.
Which characters need to be encoded in a URL?
Reserved characters with structural meaning (? # & /) and anything outside the unreserved set (letters, digits, - . _ ~) should be encoded when they appear as literal data.