How It Works

This tool encodes and decodes text using percent-encoding (also known as URL encoding) — entirely inside your browser. No data is ever sent to a server.

What is URL Encoding?

Percent-encoding is a mechanism for representing characters that are not allowed or have special meaning in a URL. Each unsafe byte is replaced with a % sign followed by two hexadecimal digits representing its value (e.g., a space becomes %20, & becomes %26).

This is used whenever you need to include arbitrary text as part of a URL query parameter or path segment without breaking the URL structure.

Implementation Details

The encoder uses JavaScript’s built-in encodeURIComponent() function, which encodes all characters except A–Z a–z 0–9 - _ . ! ~ * ' ( ).

The decoder uses decodeURIComponent(), which reverses the process. If the input contains an invalid percent-escape sequence (e.g. a lone % or a malformed sequence), the decoder will report an error rather than silently produce corrupted output.

Privacy

All encoding and decoding runs locally in your browser tab using standard JavaScript APIs. Your input text never leaves your device.