Codificador de Entidades HTML

HTML is the language of the web, but it reserves certain characters—like <, >, and &—for structural markup. If you attempt to display these characters as literal text within an HTML document, the browser will misinterpret them as tags, potentially breaking your layout or creating security holes. An HTML Entity Encoder is a critical tool that transforms sensitive characters into their safe, "Entity" equivalents (e.g., < becomes <).

The encoding engine utilizes a multi-layered mapping strategy:

1. Reserved Character Identification: The tool first scans for the "Big Five" characters required for basic security: <, >, &, ", and '.
2. Named Entity Lookup: Whenever possible, the engine uses human-readable "Named Entities" defined in the HTML5 Specification. For example, the copyright symbol © becomes ©.
3. Decimal/Hexadecimal Encoding: For characters without a standard name, the tool calculates their Unicode Code Point and represents them numerically (e.g., 🚀 for the rocket emoji).
4. Attribute vs. Content Context: The encoder can be adjusted to handle different contexts. For instance, single quotes (') must be encoded when used inside an attribute delimited by single quotes, but are safe within standard paragraph text.
5. Normalization: The tool ensures that all generated entities follow the strict &[name]; or &#[number]; format, including the mandatory trailing semicolon.

The History of HTML Entities and the W3C

The concept of Character Entities was inherited by HTML from its predecessor, SGML (Standard Generalized Markup Language). The early pioneers of the web at CERN, led by Sir Tim Berners-Lee, realized that a global communication system needed a way to represent characters from any language using only the limited ASCII character set available at the time.

The first formal entity set was defined in the HTML 2.0 Specification and has been expanded significantly by the W3C and the WHATWG to support thousands of symbols, mathematical operators, and international scripts. Today, HTML encoding is a fundamental security requirement for every Content Management System (CMS) and web application.

Technical Comparison: HTML Entities vs. URL Encoding vs. UTF-8

Understanding the difference between these transformations is essential for data integrity across the stack.

Feature	HTML Entity Encoding	URL Encoding (Percent)	UTF-8 (Raw)
Primary Goal	Document Syntax Safety	URI Transport Safety	Data Storage/Representation
Symbol	Ampersand (&)	Percent sign (%)	Multi-byte Sequence
Example	<	%3C	0x3C
Target	Browser Rendering	Address Bars / APIs	Database / Filesystems
Standard	WHATWG Living Standard	RFC 3986	ISO/IEC 10646

By using a dedicated HTML Entity Encoder, you ensure your content is rendered perfectly by the browser while protecting the underlying DOM Structure.

Security Considerations: XSS and Injection Prevention

HTML encoding is the single most important defense against Cross-Site Scripting (XSS):

• Neutralizing Script Injection: By encoding <script> into <script>, you ensure that the browser treats the input as harmless text rather than an executable command. This is the cornerstone of OWASP XSS Prevention Guidance.
• Attribute Breakouts: Encoding ensures that an attacker cannot "close" an attribute (e.g., value='...') and append a malicious handler like onmouseover.
• Client-Side Privacy: To maintain absolute Data Privacy, the entire encoding process happens locally on your computer. Your sensitive database exports or private code snippets are never transmitted to a server.