Question 1

What is an HTML entity?

Accepted Answer

An HTML entity is a text string starting with & and ending with ; that represents a special character. For example, < renders as <, & renders as &, and &copy; renders as ©. Entities prevent special characters from being interpreted as HTML markup.

Question 2

When should I encode HTML entities?

Accepted Answer

Always encode < > & " when inserting user-provided content into HTML to prevent Cross-Site Scripting (XSS) attacks. Entities are also needed for characters not available on standard keyboards and for characters with special HTML meaning.

Question 3

What is the difference between named and numeric entities?

Accepted Answer

Named entities (&copy;) are human-readable aliases. Numeric decimal entities (&#169;) and hexadecimal entities (&#xA9;) reference the Unicode code point directly. All three represent the same character. Named entities only exist for a subset of characters; numeric entities work for any Unicode character.

HTMLエンティティエンコード/デコード

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HTMLエンティティ エンコード/デコード

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HTMLエンティティエンコード/デコード