Common HTML Entities
Reserved Characters:
<→<(less than sign)>→>(greater than sign)&→&(ampersand)"→"(double quote)'→'or'(single quote)
Example Encoding:
Input: Hello & welcome!
Output: <div class="container">Hello & welcome!</div>Named vs Numeric Entities
HTML entities come in two formats:
- Named Entities: Human-readable names like
,©,€ - Numeric Entities: Unicode code points like
©(copyright ©),€(euro €)
Numeric entities use either decimal (<) or hexadecimal (<) notation. Both represent the same character but numeric entities support the entire Unicode range.
Common Use Cases
XSS Attack Prevention
HTML encoding is critical for preventing cross-site scripting (XSS) attacks. When displaying user-generated content, encoding ensures that malicious scripts are rendered as harmless text instead of executable code. For example, encoding <script>alert('XSS')</script> prevents the script from executing and displays it as visible text.
Displaying Code Examples
Technical documentation, tutorials, and developer blogs need to show HTML/XML code snippets without browsers interpreting them as actual markup. HTML encoding allows you to display tags, attributes, and complete code blocks as readable examples while preventing them from affecting page structure or rendering.
Data Storage & Transmission
When storing or transmitting HTML content in XML, JSON, or databases, special characters must be encoded to avoid breaking data structures. For instance, storing user comments that contain quotes or angle brackets requires encoding to prevent SQL injection or XML parsing errors.
Email Templates & Rich Text
Email clients vary in HTML support and special character handling. Encoding HTML entities ensures email templates display consistently across Outlook, Gmail, Apple Mail, and webmail clients. This is particularly important for symbols, currency signs, and accented characters in international emails.
Frequently Asked Questions
Does HTML encoding prevent all XSS attacks?
HTML encoding prevents most XSS attacks when applied correctly in HTML context (between tags), but it’s not sufficient for all contexts. JavaScript contexts (inside <script> tags or event handlers), CSS contexts, and URL parameters require different encoding strategies. Use context-appropriate encoding and implement Content Security Policy (CSP) headers for comprehensive XSS protection.
What’s the difference between URL encoding and HTML encoding?
URL encoding (percent-encoding) converts characters to %XX format for use in URLs (e.g., space becomes %20). HTML encoding converts characters to entity format for display in HTML (e.g., < becomes <). They serve different purposes and are not interchangeable—use URL encoding for query parameters and HTML encoding for page content.
Should I encode HTML entities in database storage?
No, store raw data in databases and encode only when displaying content. Storing encoded data causes double-encoding issues, makes data searching difficult, and complicates data migration. Encode user input during output (when rendering to HTML) rather than input (when storing to database). This principle is called “encode late, decode early.”
Related Tools
- URL Encoder/Decoder – Encode/decode URLs and query parameters
- Base64 Encoder/Decoder – Convert text and data to Base64
- JSON Formatter – Format and validate JSON data
- Regex Tester – Test regular expressions for pattern matching
Need More Developer Tools?
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