HTML Entity Encoding is the process of converting reserved characters in HTML into 'entity' representations. This is crucial for correctly displaying the HTML source code itself on a webpage, rather than having the browser render it as tags. It is also a fundamental security measure to prevent Cross-Site Scripting (XSS) attacks.

• Encode (Encode): Convert character <, >, &, ", ' etc., into corresponding HTML entities, such as <, >, &, ", '。
• Decode (Decode): Convert HTML entity strings (such as <p>）back to original HTML characters (such as <p>）。
• Secure and Reliable: This tool uses the browser's built-in DOM parser for encoding and decoding, which is the safest and most standard method, correctly handling all characters without relying on external libraries.