What it does
Web addresses may only contain a small set of characters. Spaces, accents, & and = inside a value must be written as % followed by two hex digits, such as %20 for a space. This page encodes text that way as you type, and decodes percent-encoded text back to plain words. A second box reads any address and lists its query string (the part after ?) as a table of keys and values.
Everything runs in your browser and nothing is sent anywhere. To strip tracking tags from a link first, use the link cleaner; to carry bytes rather than text, use the base64 converter.
How to use it
- Pick what the text is for: a part of an address, or a whole address.
- Type in Plain text to encode, or paste in Encoded to decode. The other box follows.
- Press Copy encoded, or Clear to start again.
- Paste a full address in Web address to see each parameter on its own row, already decoded.
What each setting does
- A part of an address (encodeURIComponent): encodes everything except letters, digits and - _ . ! ~ * ’ ( ). Use it for one search term or value.
- A whole address (encodeURI): leaves : / ? # & = alone so the address still works, and only encodes spaces and other unsafe characters.
- Spaces as +: writes spaces as + the way HTML forms do, and reads + as a space when decoding.
Worked example
Encoding a b&c=d as a part gives a%20b%26c%3Dd: the space becomes %20, & becomes %26 and = becomes %3D. Paste h%C3%A9llo%20world in Encoded and you get héllo world. As a whole address, a b&c=d becomes a%20b&c=d instead, because & and = have a meaning there.
The address https://x.com/?q=fibub&n=2 gives a table of 2 rows: q = fibub and n = 2.
FAQs
Why does it say it cannot be decoded? A % must be followed by two hex digits that make valid UTF-8. “100%” on its own or “%zz” is broken.
Which mode should I use? For a value you put after = in a link, use the part mode. Use the whole address mode only for a full link that has spaces in it.
Why is é two codes? In UTF-8, é is two bytes, so it becomes %C3%A9.
Where the numbers come from
- RFC 3986, Uniform Resource Identifier: Generic Syntax (IETF), section 2 on percent-encoding; the WHATWG URL Standard for query strings and + as a space in forms.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.