What is URL encoding?

URL encoding (also called percent encoding) is a method to encode special characters in URLs using the % symbol followed by two hexadecimal digits. This ensures URLs can be transmitted safely over the internet without ambiguity.

When should I use URL encoding?

Use URL encoding when:

• Including special characters in URLs (spaces, symbols, non-ASCII characters)
• Passing data in query parameters
• Working with API endpoints that require encoded parameters
• Handling user input that will be part of a URL
• Building dynamic URLs programmatically

What's the difference between encodeURI() and encodeURIComponent()?

encodeURI(): Encodes a complete URI, preserving protocol, domain, and path separators. Use for encoding full URLs.

encodeURIComponent(): Encodes all special characters including those that have meaning in URLs (/, ?, &, =). Use for encoding individual URL components like query parameter values.

What are reserved characters in URLs?

Reserved characters have special meanings in URLs and must be encoded when used as data:

• ! * ' ( ) ; - Sub-delimiters
• : / ? # [ ] @ - General delimiters
• $ & + , = - Special characters in query strings

How does percent encoding work?

Percent encoding replaces unsafe characters with a % followed by two hexadecimal digits representing the character's ASCII code. For example, a space (ASCII 32, hex 20) becomes %20.

What about international characters (Unicode)?

Unicode characters are first converted to UTF-8 byte sequences, then each byte is percent-encoded. For example, the character "€" (Euro sign) becomes %E2%82%AC.

Common URL encoding mistakes to avoid?

• Double-encoding: Encoding an already encoded URL
• Not encoding query parameter values
• Using encodeURI() when encodeURIComponent() is needed
• Forgetting to encode user input before including in URLs
• Not handling + signs properly (they represent spaces in query strings)

What's the maximum URL length?

While there's no official limit in the HTTP specification, practical limits exist:

• Chrome, Firefox, Safari: ~65,536 characters
• Internet Explorer: 2,083 characters
• Most web servers: 8,192 characters
• Best practice: Keep URLs under 2,000 characters for compatibility