HTML Entity Encoder/Decoder

Encode special characters to HTML entities or decode entity codes to literal text. Prevent XSS vulnerabilities and render raw code snippets safely.

HTML Source Content

Processed Output
encoded Result

Mode

encode

Input Chars

113

Output Chars

0

Entities Found

0

XSS Prevention Best Practice

Always entity-encode user submitted text before injecting it into standard HTML templates or SSR React blocks to ensure script execution cannot occur.

HTML Entity Substitution & XSS Prevention Invariants

When a web browser parses an HTML document, characters like < and > trigger DOM element creation. Escaping translates these characters into inert text entities.

1. HTML Entity Transposition Rule
Character (c)⟶&name;or&#decimal;
2. Core OWASP Sanitization Invariant
Sanitized(DOM)=∀ c ∈ { &, <, >, ", ' } ⟹ Entity(c)
Step-by-Step HTML Tag Escaping Breakdown
Step 1: Parse Raw Input String for Reserved Delimiters
Input: <script>alert("Test")</script>
Step 2: Replace Characters with Corresponding Named Entities
'<' → &lt;
'>' → &gt;
'"' → &quot;
Step 3: Render Safe Markup Representation
Safe Escaped Text=&lt;script&gt;alert(&quot;Test&quot;)&lt;/script&gt;

Standard HTML Entities Reference Table

GlyphNamed EntityDecimal EntityHex EntityStandard Purpose
&&amp;&#38;&#x26;Ampersand delimiter
<&lt;&#60;&#x3C;Tag opening delimiter
>&gt;&#62;&#x3E;Tag closing delimiter
"&quot;&#34;&#x22;Attribute value delimiter
'&#39; / &apos;&#39;&#x27;Single quote attribute delimiter

Frequently Asked Questions

What is HTML entity encoding and why is it essential?
HTML entity encoding replaces reserved structural HTML characters (like '<', '>', '&', '"', and ''') with character entity references (like '&lt;', '&gt;', '&amp;'). This instructs the browser to render the characters literally rather than executing them as DOM markup tags, eliminating Cross-Site Scripting (XSS) injection vulnerabilities.
What are the five essential characters that must be encoded for XSS security?
The OWASP security standard identifies 5 essential XML/HTML characters: Ampersand (&amp;), Less-Than (&lt;), Greater-Than (&gt;), Double Quote (&quot;), and Single Quote (&#39;).
What is the difference between Named and Numeric HTML entities?
Named entities use mnemonic strings (such as `&copy;` for ©), while numeric entities use decimal (`&#169;`) or hexadecimal (`&#xA9;`) Unicode code points. Both are parsed identically by modern HTML5 parsers.
Is HTML encoding safe for JavaScript or CSS contexts?
No. HTML entity encoding is strictly designed for HTML body and attribute contexts. Inserting data inside `<script>` or `<style>` blocks requires JavaScript-string escaping or JSON serialization, respectively.

Related Tools