URL Encoder and Decoder

How percent-encoding works

A URL may contain only a limited set of ASCII characters. Any other character, and any character that has a special meaning where it appears, is written as a % sign followed by two hexadecimal digits for each byte (RFC 3986, section 2.1). Characters outside ASCII are first turned into UTF-8 bytes: ₹ (U+20B9) is the three bytes E2 82 B9, so it becomes %E2%82%B9. The tool writes upper-case hex digits, as RFC 3986 recommends.

Which mode to use

• Component works like JavaScript's encodeURIComponent. It leaves A–Z a–z 0–9 - _ . ! ~ * ' ( ) as they are and encodes everything else. Use it for one value: a query parameter, a form field or a path segment.
• Full URL works like encodeURI. It also leaves ; , / ? : @ & = + $ # alone, so a complete address that contains spaces or non-English text keeps its structure.
• Form writes data the way URLSearchParams does, in the application/x-www-form-urlencoded format that HTML forms also send. It leaves A–Z a–z 0–9 * - . _ alone and turns a space into +.
• Non-ASCII only leaves every ASCII character alone, including spaces and existing %XX sequences, and encodes the rest. Use it for an address that is otherwise ready but contains Hindi or other non-English letters, or one that is already partly encoded.

The difference between Component and Full URL matters. Full URL keeps & = ? / and # because they separate the parts of an address. Used on a single value such as Tom & Jerry, it leaves the & in place (Tom%20&%20Jerry), and the value is split in two. Component encodes it as %26 (Tom%20%26%20Jerry), which is why it is the right choice for values.

The strict option also encodes ! ' ( ) *, leaving only the unreserved characters of RFC 3986, section 2.3 (A–Z a–z 0–9 - . _ ~). OAuth 1.0 signatures and AWS Signature Version 4 query strings expect this form.

Worked example

The value नई दिल्ली & co in Component mode becomes:

%E0%A4%A8%E0%A4%88%20%E0%A4%A6%E0%A4%BF%E0%A4%B2%E0%A5%8D%E0%A4%B2%E0%A5%80%20%26%20co

Each Devanagari letter or sign takes three UTF-8 bytes, so it turns into three %XX groups. In Form mode the three spaces become + instead of %20.

Decoding

Decoding reads each %XX as a byte and the bytes as UTF-8 text. When a % is not followed by two hex digits, or the bytes are not valid UTF-8, the tool stops and names the position. A common cause is %E9 on its own: older systems wrote é that way in Latin-1, while UTF-8 uses %C3%A9. Switch on Leave malformed sequences as they are to decode everything else.

A + is turned into a space only when you ask for it, because in a path + is a real plus sign. Decode repeatedly handles text that was encoded twice, such as %2520: %25 is the % sign, so the first round gives %20 and the second a space. Decoded control characters such as %00 (null) are kept, and the page points them out, because the output box shows them as a blank or a box.

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