How do I decode a URL?

Paste the encoded text and the decoded version appears. %20 becomes a space, %2F becomes / and so on.

Should a plus sign become a space?

In an HTML form query string, yes. Elsewhere in a URL a + is a literal plus sign. Tick the option only for form-style data.

A % that is not followed by two hex digits is left as it is, instead of stopping with an error.

It decodes like decodeURI, so reserved characters such as %2F and %3F stay encoded and the structure of the URL is kept.

Decode percent-encoded URLs and query strings online. Treats + as a space if you like and leaves malformed sequences untouched.

Paste encoded text to decode it. Full URL mode keeps reserved characters such as %2F and %3F encoded, like decodeURI.

How do I decode a URL?: Paste the encoded text and the decoded version appears. %20 becomes a space, %2F becomes / and so on.
Should a plus sign become a space?: In an HTML form query string, yes. Elsewhere in a URL a + is a literal plus sign. Tick the option only for form-style data.
What happens to malformed sequences?: A % that is not followed by two hex digits is left as it is, instead of stopping with an error.
What does Full URL mode do?: It decodes like decodeURI, so reserved characters such as %2F and %3F stay encoded and the structure of the URL is kept.