HTML Entity Encoder
Convert special characters to HTML entities and back. Protect your code from XSS attacks and ensure proper HTML rendering.
Common Entities
Tip: Click any entity to copy it to clipboard
Free HTML Entity Encoder & Decoder: Complete XSS Prevention Guide
Professional HTML entity conversion tool for web developers. Encode special characters, prevent cross-site scripting attacks, and ensure secure HTML rendering in production applications.
What Are HTML Entities and Why They Matter for Web Security
HTML entities are escape sequences that represent special characters in web documents. According to the WHATWG HTML Living Standard, these entities prevent browsers from interpreting characters like <, >, and & as HTML markup. Professional web developers use entity encoding to stop OWASP-documented XSS attacks and display user-generated content safely.
How HTML Entity Encoding Works:
- Character Recognition: Parser identifies special characters requiring encoding
- Entity Selection: Converts to named (<), decimal (<), or hex (<) format
- Safe Output: Browser renders entity as text instead of executing as markup
- Bidirectional Conversion: Supports encoding text to entities and decoding back
Essential HTML Entities:
Three Entity Formats:
- ✓Named Entities: < © € (human-readable)
- ✓Decimal Entities: < © (universal support)
- ✓Hex Entities: < © (compact format)
Preventing Cross-Site Scripting (XSS) Attacks with HTML Entity Encoding
The XSS Vulnerability Problem
Cross-site scripting remains in the OWASP Top 10 security risks. Without proper HTML entity encoding, attackers inject malicious JavaScript through form inputs, URL parameters, or comment sections. This compromises user sessions, steals credentials, and executes unauthorized actions.
Vulnerable Code:
<script>document.cookie</script>Executes malicious script
Secure Output:
<script>document.cookie</script>Displays as harmless text
Security Benefits
- • Blocks XSS injection vectors
- • Prevents HTML tag insertion
- • Stops script execution in inputs
- • Protects form submissions
- • Sanitizes database content
Display Benefits
- • Renders code examples correctly
- • Handles Unicode characters
- • Preserves special symbols
- • Maintains email formatting
- • Cross-browser compatibility
Compliance Benefits
- • OWASP security compliance
- • PCI-DSS requirements
- • SOC 2 audit preparation
- • Penetration test readiness
- • Industry standard practice
Real-World HTML Entity Encoding Use Cases
Web Application Security
- Comment Systems: Encode blog comments and forum posts before rendering
- Form Validation: Sanitize user input from contact forms and surveys
- Documentation: Display code snippets without execution risk
- Email Templates: Encode dynamic variables in HTML emails
- API Integration: Sanitize third-party API responses
- CMS Platforms: Handle WYSIWYG editor output securely
Data Processing Tasks
- Database Storage: Encode before INSERT/UPDATE operations
- XML/RSS Feeds: Comply with XML character restrictions
- CSV Export: Handle commas and quotes in data files
- JSON APIs: Escape HTML in JSON string values
- Template Rendering: Sanitize Jinja2, Handlebars variables
- Log Files: Prevent log injection attacks
Industry-Specific Applications
E-commerce
- • Product descriptions
- • Customer reviews
- • Order emails
- • Currency symbols
- • Search queries
Content Management
- • Blog content
- • User profiles
- • Comment moderation
- • SEO metadata
- • i18n content
SaaS Applications
- • Dashboard widgets
- • User notifications
- • Config editors
- • Analytics reports
- • Webhook payloads
Complete HTML Character Entity Reference
Essential Characters
Required encoding for W3C HTML5 specification compliance:
Extended Characters
International and typographic characters:
Mathematical Symbols
Math operators and Greek letters:
Encoding Mode Selection Guide
Essential Only
Encode < > & " ' only
Use for: User input sanitizationExtended Mode
Include accents and symbols
Use for: Multilingual contentAll Non-ASCII
Characters above 127
Use for: Maximum compatibilityHTML Entity Encoding Best Practices for Production Systems
When to Always Encode
✓ Mandatory Encoding Scenarios
- • All user-submitted content
- • External API responses
- • Database query results
- • Email template variables
- • URL parameters in HTML
- • Form input display values
⚠ Context-Specific Encoding
- • Rich text editor (selective)
- • JSON strings (different escaping)
- • JavaScript variables (JS escaping)
- • Trusted admin content (evaluate risk)
Common Implementation Mistakes
✗ Avoid These Errors
- • Double-encoding already escaped text
- • Client-side only validation (bypassable)
- • Regex-based sanitization (incomplete)
- • Forgetting template auto-escaping
- • Mixing HTML and JavaScript contexts
ℹ Professional Tips
- • Test with OWASP XSS payloads
- • Use framework built-in functions
- • Encode at output, validate at input
- • Document your encoding strategy
Defense-in-Depth Security Strategy
HTML entity encoding is one security layer. The OWASP XSS Prevention Cheat Sheet recommends combining multiple defenses:
1. Input Validation
Whitelist allowed characters and patterns
2. Context-Aware Encoding
HTML, JavaScript, URL, CSS escaping
3. Security Headers
Content-Security-Policy, X-XSS-Protection
Frequently Asked Questions About HTML Entity Encoding
How does HTML entity encoding differ from URL encoding?
HTML encoding uses entities like < for < to safely display content in HTML documents. URL encoding uses percent-encoding like %3C for URLs and query strings. Each serves different contexts per RFC 3986. Never interchange them - HTML entities break in URLs, and percent-encoding displays literally in HTML.
Which entity format should I use: named, decimal, or hexadecimal?
Named entities (<) are human-readable for common characters but limited to ~2,000 predefined names. Decimal (<) and hexadecimal (<) work for any Unicode character with universal browser support. Use named for readability in frequently edited code, numeric for programmatic encoding and rare characters. All three are valid per HTML5 specification.
Does HTML entity encoding completely prevent XSS attacks?
HTML entity encoding prevents XSS in HTML content contexts but isn't sufficient alone. JavaScript contexts need JavaScript escaping, URLs need percent-encoding, and CSS needs CSS escaping. Implement context-appropriate encoding plus Content-Security-Policy headers. Review the Google CSP Evaluator for comprehensive protection.
Should I store HTML entities in my database or encode during output?
Best practice: store original data, encode during output. This prevents double-encoding issues and allows context-appropriate escaping (HTML vs JSON vs plain text). Store validated but unencoded user input, then apply proper escaping based on output context. This approach offers maximum flexibility and prevents data corruption from repeated encoding.
Is this HTML entity encoder free to use for commercial projects?
Yes, completely free with unlimited usage for personal and commercial projects. No registration, subscriptions, or hidden costs. Client-side processing ensures your data stays private. Process unlimited text for development, production systems, and client work without restrictions.
Can I use this tool for XML and RSS feed encoding?
Yes. HTML entities work in XML and RSS since they share entity syntax per W3C XML specification. The five essential characters (< > & " ') must be encoded in XML. Use "Essential Only" mode for XML/RSS compliance, or "Extended" mode for additional character support in content elements.