URL Encoding Explained: Why and How to Encode URLs
Learn what URL encoding is, why it matters, and how to properly encode URLs for web development.
URL encoding, also known as percent-encoding, is a mechanism for encoding special characters in URLs. Understanding URL encoding is essential for web developers, API integrators, and anyone working with web addresses.
What Is URL Encoding?
URLs can only contain a specific set of characters from the ASCII character set. When a URL needs to contain characters outside this set (like spaces, special symbols, or non-English characters), those characters must be encoded.
URL encoding replaces unsafe characters with a percent sign (%) followed by two hexadecimal digits. For example:
- Space becomes %20
- & becomes %26
- = becomes %3D
- ? becomes %3F
Why URL Encoding Matters
Without proper encoding, URLs can break or be misinterpreted. For example, a space in a URL could be interpreted as the end of the URL. The & character could be interpreted as a parameter separator rather than part of a value.
Common Characters That Need Encoding
| Character | Encoded | Reason |
|---|---|---|
| Space | %20 or + | Separates URL parts |
| & | %26 | Parameter separator |
| = | %3D | Key-value separator |
| ? | %3F | Query string start |
| # | %23 | Fragment identifier |
| / | %2F | Path separator |
| + | %2B | Means space in queries |
encodeURI vs encodeURIComponent
In JavaScript, there are two encoding functions:
- encodeURI() encodes a complete URI but preserves characters that have special meaning in URLs (like /, ?, #)
- encodeURIComponent() encodes everything, making it suitable for encoding parameter values
Use encodeURIComponent() for query parameters and encodeURI() for complete URLs.
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