HTML Encoder/Decoder

Encode or decode HTML entities and special characters. Convert ampersands, angle brackets, quotes, and apostrophes to their HTML entity equivalents and back.

What Is HTML Encoding?

HTML encoding (also called HTML escaping) is the process of converting special characters into their corresponding HTML entity equivalents. For example, the less-than sign < becomes &lt;, and an ampersand & becomes &amp;. This ensures that browsers display these characters as literal text rather than interpreting them as HTML markup.

Why HTML Encoding Matters for Security

HTML encoding is a critical defense against Cross-Site Scripting (XSS) attacks. When user-generated content is displayed on a web page without proper encoding, attackers can inject malicious scripts that execute in other users' browsers. Encoding special characters neutralizes this threat by rendering injected code as harmless text. Always encode dynamic content before inserting it into HTML documents.

Encoding vs. Decoding

Encoding converts characters to entities for safe display, while decoding converts entities back to their original characters. Use encoding when outputting user content to a web page. Use decoding when reading HTML source or processing data that contains encoded entities. Common encoded characters include ampersands, angle brackets, quotes, and apostrophes.

Common Use Cases

  • Displaying code examples in blog posts and documentation
  • Sanitizing user-generated content in comments and forms
  • Preparing data for email templates and newsletters
  • Working with XML or other markup languages that share HTML entities

Frequently Asked Questions

What is HTML encoding?
HTML encoding converts special characters into their HTML entity equivalents. For example, < becomes &lt; and & becomes &amp;. This prevents characters from being interpreted as HTML markup and helps prevent XSS attacks.
Why should I encode HTML?
HTML encoding is essential for security (preventing XSS attacks), displaying code examples on web pages, ensuring user-generated content renders safely, and meeting accessibility standards. Always encode dynamic content before inserting it into HTML.
What are common HTML entities?
The most common HTML entities are: &amp; (&), &lt; (<), &gt; (>), &quot; ("), &#39; ('), &#x27; ('), and &#x2F; (/). There are hundreds of named entities including &copy; (copyright), &reg; (registered), and &euro; (euro).
Is HTML encoding the same as URL encoding?
No. HTML encoding converts characters for safe display in HTML documents using &-based entities. URL encoding (percent-encoding) converts characters for safe transmission in URLs using %-encoded values. Different contexts require different encoding types.
Does HTML encoding prevent XSS attacks?
Yes, proper HTML encoding is one of the most effective defenses against Cross-Site Scripting (XSS) attacks. By encoding user input before inserting it into HTML, you prevent attackers from injecting malicious scripts.
What characters need to be HTML-encoded?
Five characters must always be encoded in HTML: & (ampersand), < (less than), > (greater than), double quote ("), and single quote ('). Other non-ASCII characters can optionally be encoded as named or numeric entities for broader compatibility.