HTML Entities

Table of Content

Introduction to HTML Entities

HTML Entities: What Are They?

Think of HTML entities as the building blocks of web pages. They're tiny codes that represent special characters, like accented letters (like é or ñ) or symbols (like © or ™). They make sure that these characters display correctly on your screen, no matter what device or browser you're using.

History of HTML Entities

HTML entities have been around for a long time, since the early days of the web. Back then, computers couldn't handle all the different characters used in different languages. So, the creators of HTML came up with these codes to represent them.

Importance for Web Development

HTML entities are essential for creating websites that can be read and understood by everyone. They make sure that:

  • Different characters display correctly: Whether it's an accented letter in a French article or a rupee symbol in an Indian online store, HTML entities make sure they show up as they should.
  • Website content is accessible: For people using screen readers (which help them understand web content), HTML entities provide important clues about the pronunciation of special characters.

Importance for Content Accessibility

HTML entities also play a crucial role in making web content accessible to people with disabilities. For instance, if a blind person is using a screen reader, HTML entities can help the reader understand that "©" stands for "copyright."

Making It Simple for Everyone

Imagine you're writing a story about a trip to Paris. You want to use the French word "éclair" (a delicious pastry). Without HTML entities, your computer might show it as a weird-looking question mark. But by using the code "é" (which represents the letter "é"), you can make sure it displays correctly. That way, everyone reading your story, regardless of their language or device, can enjoy the full experience.


Types of HTML Entities

Character Entities:

Imagine some special characters like '<', '>', and ' ' (space) that might cause problems in coding. Character entities are like a secret code that lets you represent these characters safely. For example, '<' becomes '&lt;', '>' becomes '&gt;', and ' ' becomes '&nbsp;'. This way, they can be used in code without causing issues.

Symbol Entities:

Think of symbols like copyright © or trademark ™. Symbol entities are special codes that let you display these symbols in your code. For example, '&copy;' represents the copyright symbol and '&trade;' represents the trademark symbol.

Emoji Entities:

Emojis are like cute little pictures we use to express ourselves. Emoji entities are codes that let you display emojis in your code. For example, '&#128512;' shows a smiling face emoji. This makes it fun and expressive to use in code, just like in messages!


Character Encoding

Numeric Entity References

Numeric Entity References are used to represent characters that cannot be entered directly in a document. They are identified by a number sign (#) followed by a decimal or hexadecimal number.

Decimal Entity References

Decimal entity references use the format:

&#DecimalNumber;

For example, the entity reference for an ampersand (&) character is:

&#38;

Hexadecimal Entity References

Hexadecimal entity references use the format:

&#xHexadecimalNumber;

For example, the entity reference for a copyright symbol (©) character is:

&#x00A9;

Using Numeric Entity References

To use a numeric entity reference, simply insert the appropriate entity reference code into your document. For example, to insert an ampersand (&) character, you would use the following code:

&amp;

Benefits of Using Unicode Character Sets

Unicode character sets are a way to represent all of the characters in the world in a single, unified code system. This makes it possible to exchange text and data between different languages and systems without having to worry about character encoding issues.

Benefits of Using Entity Names

Entity names are a way to represent characters in a more human-readable format. For example, the entity name for an ampersand (&) character is "amp". This makes it easier to read and understand your code.


Common HTML Entities

Special Symbols for Different Uses:

Less Than (<) and Greater Than (>)

  • Used to compare things or numbers. For example, 5 < 10 means "5 is less than 10".

Ampersand (&)

  • Short for "and". For example, "John & Mary" means "John and Mary".

Double Quotes ("") and Single Quote (')

  • Used to show the exact words that someone said or wrote. For example, "He said, 'Hello'."

Non-Breaking Space ( )

  • Used to create a small space that won't break into a new line. For example, it can be used to separate words like "First" and "Name" in a form.
  • Indicates that something is protected by copyright laws. For example, © 2023 XYZ Company.

Trade Mark Sign (™)

  • Indicates that a word, phrase, or symbol is a trademark. For example, ™ Coca-Cola.

Trademark TM Symbol (™)

  • Similar to the Trade Mark Sign, but less commonly used.

At Symbol (@)

  • Used to represent an email address. For example, yourname@email.com.

At the Rate Symbol (@)

  • An old-fashioned version of the At Symbol.

Usage and Best Practices

Inserting Entities into HTML

Entities are special characters that can be used in HTML to represent characters that cannot be typed directly. For example, the entity &copy; represents the copyright symbol (©).

To insert an entity into HTML, use the following syntax:

&name

where name is the name of the entity. For example, to insert the copyright symbol, you would use the following code:

©

Encoding Special Characters for Accessibility

Some special characters can be difficult or impossible for people with disabilities to see or read. For example, the character > can be difficult to see for people with low vision, and the character * can be difficult to read for people with dyslexia.

To make your HTML accessible, you should encode special characters using entities. This will ensure that all users can see and read your content.

Avoiding Ambiguous and Deprecated Entities

Some entities are ambiguous, meaning that they can represent multiple characters. For example, the entity &amp; can represent either the ampersand symbol (&) or the logical AND operator (&&).

Other entities are deprecated, meaning that they are no longer recommended for use. For example, the entity &nbsp; is deprecated in favor of the CSS property white-space: nowrap.

You should avoid using ambiguous and deprecated entities in your HTML.

Using Entities for Symbols and International Characters

Entities can be used to represent symbols and international characters that are not available on your keyboard. For example, the entity &euro; represents the euro symbol (€).

To find the entity for a particular symbol or character, you can use an online entity reference tool.

Example

The following HTML code inserts a copyright symbol, encodes the greater than sign, and uses an entity to represent the euro symbol:

<p>Copyright © 2023 > 100 €</p>

Differences from Other Character Encodings

HTML Entities

Imagine you're writing a website with a special character, like the copyright symbol ©. Instead of typing the actual symbol, you can use an HTML entity like ©. This tells the browser to display the copyright symbol instead of the text "©".

ASCII Codes

ASCII codes are numbers that represent characters. For example, the ASCII code for the lowercase "a" is 97. Computers use ASCII codes to store text, but they're not as readable as HTML entities.

URL Encoding

When you enter a website address (URL) into your browser, it gets encoded using URL encoding. This replaces certain characters with special characters, such as spaces being replaced by "%20". This makes the URL easier for the browser to understand.

Unicode Code Points

Unicode is a system that assigns a unique number to every character in the world. A Unicode code point is the number that represents the character. For example, the Unicode code point for the copyright symbol is U+00A9.

Comparison

| Feature | HTML Entities | ASCII Codes | URL Encoding | Unicode Code Points | |---|---|---|---|---| | Readability | High | Low | Low | Very High | | Used for | Displaying special characters on websites | Storing text on computers | Encoding URLs | Representing all characters in the world | | Example | © | 97 | %20 | U+00A9 |

In summary, HTML entities are easy to read and used for displaying special characters on websites. ASCII codes are used for storing text on computers, while URL encoding is used for encoding URLs. Unicode code points are the most comprehensive way to represent all characters in the world.


Common Mistakes and Troubleshooting

Mismatched Entity Names

Imagine you have a story about two friends, Tom and Jane. But in some parts of the story, Tom is called "Timmy" and Jane is called "Jenny." That's confusing! Similarly, in coding, entities are named consistently to avoid confusion.

Incorrect Numeric References

Numbers should be referenced correctly. If you write something like "–5", the computer might interpret it as "–5" (with a dash) instead of "−5" (with a minus sign).

Entities Not Displaying Properly

Sometimes, special characters or symbols don't display correctly. For example, if you want to show the Euro sign "€", you need to use a special code (€). Otherwise, it might appear as a question mark or an empty box.

Fixing Encoding Errors in Browsers

When you open a web page, your browser needs to know how to interpret the characters on the page. If the encoding is wrong, it can show symbols or characters instead of the intended text. To fix this, you can check the encoding settings in your browser and ensure they match the encoding used in the web page.

Simplified Example

Imagine you have a recipe for pizza. The ingredient list says "2 cups of flour." If you mistakenly add 2 spoons of flour, the pizza will turn out wrong. Similarly, if you make mistakes in coding, your program might not work correctly. By following these guidelines, you can improve the readability and accuracy of your code.


Advanced Techniques

Custom Entity Definitions (XHTML)

Imagine a special type of code that allows you to use special characters or symbols in your webpages. These codes are called "entities."

Entity Expansion

When you use an entity code in your webpage, it gets replaced by the actual character it represents. For example:

&amp;

This code gets replaced by the ampersand symbol (&). It's like using a secret shortcut to write the ampersand.

Entity Normalization

Sometimes, special characters can appear in different forms in a webpage. For instance, the ampersand can be written as "&" or "&".

Entity normalization makes sure that all these different forms are converted to the same standard form. This helps ensure that your webpage displays correctly across different browsers.

Using Entities for Dynamic Content

Entities can be used to display dynamic content on a webpage. This means you can change the content of your page without changing the HTML code.

For example, you could have an entity that represents the current date:

&date;

Then, you can use this entity in your webpage:

<h1>Today's Date: &date</h1>

When the webpage is loaded, the entity "&date" will be replaced with the actual date.

Benefits of Using Entities:

  • Readability: Entities make your webpages easier to read and understand.
  • Flexibility: They allow you to easily change the content of your pages without editing the code.
  • Standardization: Entities ensure that special characters are displayed consistently across browsers.