What is URL Decoding?
URL decoding (percent decoding) converts percent-encoded characters back to their original form. It reverses the URL encoding process, replacing %XX sequences with their corresponding characters.
When to Decode URLs
- Reading Query Parameters: Decode values from URL query strings
- Log Analysis: Make encoded URLs in logs readable
- Debugging: Understand what data is being sent in URLs
- Data Processing: Extract and process URL parameters
- Search Analysis: Read encoded search queries
- API Development: Debug API requests with encoded parameters
Common Encoded Characters
- %20 or + → Space
- %21 → !
- %22 → "
- %23 → #
- %24 → $
- %26 → &
- %3D → =
- %3F → ?
- %40 → @
Examples
Encoded: Hello%20World%21
Decoded: Hello World!
Encoded: user%40example.com
Decoded: user@example.com
Encoded: search%3Fq%3Dhello%2Bworld
Decoded: search?q=hello+world
Security Considerations
⚠️ Security Notes
- Always validate and sanitize decoded data
- Be aware of double-encoding attacks
- Watch for malicious payloads in encoded URLs
- Don't trust user-provided encoded data
- Implement proper input validation after decoding
Common Issues
- Malformed encoding: Invalid %XX sequences will cause errors
- Double encoding: Data encoded multiple times needs multiple decodes
- Plus signs: + may represent space in query strings
- Character sets: Ensure proper UTF-8 handling for international characters