Rechnerpilot tool

URL Encoder

Encode text as a percent-encoded URL component (RFC 3986) or decode it back – locally in your browser.

Developer Tools

Enter text to encode it.

Explanation

How URL Encoder works

URL encoding (percent-encoding) is defined in RFC 3986. It ensures that characters which have a special meaning in a URL or are not allowed can be transmitted safely. Each affected character is represented as a % sequence of its UTF-8 bytes (e.g. a space as %20, “ß” as %C3%9F).

This tool encodes a single URL component (such as a query value), not a whole URL. Reserved characters like &, ?, = and / are therefore deliberately encoded so they form no URL structure.

Limits of this tool

Component encoding — not intended for encoding complete URLs with structure.
Strictly RFC 3986 — “+” is not interpreted as a space.
No privacy — percent-encoding is trivially reversible.

Sources

RFC 3986: Uniform Resource Identifier (URI): Generic Syntax. IETF, 2005. rfc-editor.org/rfc/rfc3986 (Retrieved: 2026-09-09).
WHATWG URL Standard: Definition of percent-encoding in the browser. url.spec.whatwg.org (Retrieved: 2026-09-09).

Practice

Practical examples

Encode a search term

“Straße & Weg” becomes “Stra%C3%9Fe%20%26%20Weg” for use in a URL.

Decode a parameter

“%C3%BCber%20uns” is reproducibly turned back into “über uns”.

Special characters

Reserved characters like & ? = / are percent-encoded so they take on no URL meaning.

FAQ

Frequently asked questions

What is URL encoding (percent-encoding)?

URL encoding replaces characters that have special meaning in a URL or are not allowed with % sequences of their UTF-8 bytes. Defined in RFC 3986.

Which characters remain unchanged?

The “unreserved” characters per RFC 3986: A–Z, a–z, 0–9 and - _ . ~. All other characters are percent-encoded.

Is the text sent to a server?

No. Encoding happens locally in the browser with encodeURIComponent or decodeURIComponent. No data is transmitted.

Why is “+” not decoded as a space?

“+” as a space is a peculiarity of form encoding (application/x-www-form-urlencoded), not of RFC 3986. This tool decodes strictly per RFC 3986; spaces are %20.

When does decoding fail?

For invalid or incomplete percent sequences (e.g. “%ZZ” or “%A”), the decoder reports an error because there are no valid UTF-8 bytes.

Tips

Good to know

For whole URLs, component encoding is only suitable for individual parts (query values).
Reserved characters (& ? = /) are deliberately encoded so they form no URL structure.
Spaces become %20, not +.

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