URL encoder and decoder — encodeURIComponent or encodeURI, both ways

How to use the URL encoder and decoder

1. Paste text into Text. The default is a sample search URL with accents and spaces.
2. Choose Mode: Encode or Decode.
3. Choose Scope: Component (encodeURIComponent) or Full URL (encodeURI).
4. Tick Spaces as + (form encoding) if you need form-style spaces.
5. Copy the Encoded or Decoded result.

What it does and when to use it

URLs may only contain a limited set of ASCII characters. Everything else, from spaces and & to é and emoji, must be written as % followed by hex bytes. Use this tool when you build a link by hand, debug a redirect that loses part of its query string, read an encoded value from a server log, or check what your code should produce.

To build a full query string from key–value pairs, use the query string builder, or turn a JSON object into one with JSON to query string. To split a URL into protocol, host, path and parameters, use the URL parser.

How it works

Text is converted to UTF-8 bytes, and each byte outside the allowed set is written as %XX, as described in RFC 3986. The tool calls JavaScript’s built-in functions in your browser:

• Component uses encodeURIComponent and decodeURIComponent. Reserved characters such as / ? & = # are escaped too.
• Full URL uses encodeURI and decodeURI. Reserved characters are kept, and when decoding, escapes such as %2F and %26 stay as they are.
• Spaces as + swaps %20 for + after encoding, and swaps + for a space before decoding.

Worked examples

Component mode on a value with reserved characters, a b&c=d/é:

a%20b%26c%3Dd%2F%C3%A9

é becomes two bytes, %C3%A9, because UTF-8 uses two bytes for it.

Full URL mode on the default sample shows the classic trap:

Input:  https://example.com/search?q=café & crème&page=2
Output: https://example.com/search?q=caf%C3%A9%20&%20cr%C3%A8me&page=2

The & inside the search term is left as is, so a server reads q=café and a stray parameter crème. Encode the value café & crème in Component mode instead, which gives caf%C3%A9%20%26%20cr%C3%A8me.

Decoding form data with Spaces as + ticked, caf%C3%A9+au+lait gives café au lait.

Limits and tips

• Encode once. Running encoded text through again turns %20 into %2520. If you see %25 in a URL, something encoded twice.
• No validation. The tool does not check that a URL is well formed or that its host exists.
• Decoding can change meaning. Decoding a whole URL in Component mode turns %26 into a real &, which splits the value.