Why do I see a malformed encoding error?

The input contains a percent sign that is not followed by two valid hex digits, so it is not valid percent-encoding. Check for stray % characters or truncated sequences.

Which mode should I use?

Component mode (decodeURIComponent) decodes every escape sequence and suits a single query value. Full-URL mode (decodeURI) leaves reserved characters like : / ? & # untouched.

Is my data uploaded anywhere?

No. Decoding runs entirely in your browser using built-in functions — nothing is sent to any server.

What is percent-encoding?

Percent-encoding (URL encoding) represents reserved or non-ASCII characters as a % sign followed by two hexadecimal digits of the character's UTF-8 byte value. So a space becomes %20 and a slash becomes %2F. Decoding reverses this back to the original character.

What does %20 decode to?

%20 decodes to a single space character. The hex 20 is 32 in decimal, which is the ASCII/UTF-8 code for a space.

Does a plus sign decode to a space?

Not with these functions. decodeURIComponent and decodeURI leave + unchanged; the + means a space only in the older application/x-www-form-urlencoded form encoding, not in standard URI percent-encoding.

How are non-ASCII characters like é decoded?

They are stored as their UTF-8 bytes, each percent-encoded. The letter é is %C3%A9, two bytes that decodeURIComponent reassembles into the single character é.

When should I use full-URL mode over component mode?

Use full-URL mode (decodeURI) when you have a whole URL and want to keep its structure readable while leaving separators like : / ? & # intact. Use component mode (decodeURIComponent) when decoding a single piece such as one query value or path segment.

URL Decoder — Gera Tools

URL decoder

Percent-encoding (also called URL encoding) is how URLs carry spaces, punctuation and non-English characters safely: each one is written as a % followed by two hexadecimal digits, so a space becomes %20 and a slash becomes %2F. This decoder reverses that, turning an encoded string or query parameter back into readable text — useful for inspecting links, debugging API requests, or reading logged URLs.

How it works

The tool uses the browser’s two built-in decoding functions:

Component mode — decodeURIComponent decodes every escape sequence, including reserved characters like : / ? & #. Use it for a single piece such as one query value or path segment.
Full-URL mode — decodeURI decodes the same percent sequences but leaves reserved URL separators untouched, so a whole URL keeps its structure.

Each %XX is interpreted as a UTF-8 byte, so multi-byte characters (like é, stored as %C3%A9) are reassembled correctly. A % that is not followed by two valid hex digits is malformed and raises an error.

Example

The encoded value name%3DJohn%20Doe%26city%3DZ%C3%BCrich decodes in component mode to name=John Doe&city=Zürich: %3D becomes =, %20 a space, %26 an ampersand, and %C3%BC the character ü.

Encoded	Decoded
%20	(space)
%2F	/
%3D	=
%26	&
%C3%A9	é

It all happens in your browser with built-in functions — nothing is uploaded. To encode again, use the URL encoder.