HTML Entity Encoder/Decoder: Convert Special Characters Instantly

The Problem: HTML's Interpretation of Special Characters

HTML (HyperText Markup Language) is designed to interpret certain characters as structural elements, not as literal text. The most common examples are:

• < (less than): Used to start an HTML tag (e.g., <div>, <p>).
• > (greater than): Used to close an HTML tag.
• & (ampersand): Used to start a character entity itself.
• " (quotation mark): Used to define attribute values.
• ' (apostrophe): Also used to define attribute values.

If you were to simply type these characters directly into your HTML content, the browser might misinterpret them. For instance, if you wanted to write "5 < 10" on your webpage, the browser might think "< 10" is the start of an unrecognized tag and display it incorrectly or not at all.

The Solution: Character Entities

To prevent this misinterpretation, HTML provides character entities. These are essentially placeholders that represent the actual characters.

Two Forms of Character Entities:

1. Named Entities (&entity_name;):

   • These use human-readable names to represent characters.
   • For example, < represents the less-than sign, > represents the greater-than sign, and & represents the ampersand.
   • Named entities are generally easier to remember and read.

2. Numeric Entities (&#entity_number;):

   • These use numeric codes (either decimal or hexadecimal) to represent characters.
   • For example, < (decimal) and < (hexadecimal) both represent the less-than sign.
   • Numeric entities are useful for representing characters that don't have named entities, including characters from various alphabets and symbols.

Why Use Character Entities?

• Displaying Reserved Characters: As explained, this is the primary reason.
• Displaying Invisible Characters:
  • For example,   represents a non-breaking space. This prevents the browser from collapsing multiple spaces into a single space, which is useful for formatting.
• Displaying Characters Not Easily Typed:
  • Character entities allow you to display symbols and characters that may not be available on your keyboard or that require special input methods.
  • For example, copyright symbols, currency symbols, and special language characters.
• Ensuring Consistent Display: Character entities help ensure that characters are displayed consistently across different browsers and operating systems.

Practical Examples:

• "To check if a is less than b, write: a < b."
• "Copyright © 2023."
• "A space that will not break onto a new line: word1 word2."
• "the Euro symbol : €"

Key Considerations:

• While named entities are generally preferred for readability, numeric entities offer greater flexibility and support a wider range of characters.
• Modern HTML5 has improved support for Unicode characters, reducing the need for some character entities. However, they remain essential for reserved characters and for ensuring compatibility with older browsers.
• When working with user generated content that will be displayed on a webpage, it is extremely important to sanitize the user input, and convert special characters to their entity form. This helps to prevent malicious users from injecting code into your web pages.

By using character entities, you can ensure that your HTML content is displayed correctly and consistently, regardless of the characters it contains.

Encoding

Encode operations converts any reserved character into its character entity equivalent.

Decoding

Decode does the reverse job; converting any character entity into its canonical representation.

Sources:
[1] Official list of character entities
[2] www.w3schools.com/html/html_entities.asp
[3] developer.mozilla.org/en-US/docs/Glossary/Entity
[4] Learn HTML