Encode and decode URLs

Web addresses only allow a limited set of characters. Spaces, accents, ampersands and question marks must be replaced before travelling across the network.

This tool applies and reverses that substitution.

Each disallowed character is replaced by a percent sign followed by its hexadecimal value in UTF-8. A space, for instance, becomes %20.

Reserved characters have a job to do

The question mark separates path from parameters, the ampersand separates parameters from one another, the equals sign joins name and value, the hash marks a fragment. If one of those symbols appears inside a value unencoded, the browser reads it as structure and the address breaks. Encoding turns it into data.

Why an accent takes two sequences

Encoding works on bytes, not letters. In UTF-8 an accented letter takes two bytes, and each byte becomes a percent sign plus two digits. That is why ñ appears as two groups and an emoji can take four.

The space has two forms

In a path it is encoded as percent twenty. In form data sent with the classic method a plus sign is used. Both are correct in context, and mixing them produces subtle errors where spaces turn into literal plus signs.

Do not put personal data in the address

Addresses are recorded in browser history, in server logs and in referrer headers sent to third parties. Any sensitive data belongs in the body of a request, never in the query string.