What’s the Difference Between HTML and XML?


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What’s the difference between HTML and XML? What are the similarities between HTML and XML? Main syntax differences: HTML vs. XML Other key differences: HTML vs. XML When to use HTML vs XML How to use HTML and XML together Summary of key differences: HTML vs. XML How can AWS support your HTML and XML requirements?

What’s the difference between HTML and XML?

HTML and XML are two popular markup languages in application development and web development. Even though they have similar names, they have different use cases. HTML is primarily used to develop an application’s UI. It renders the text, images, buttons, checkboxes, and dropdown boxes seen on a website or application. In contrast, the primary purpose of XML is the exchange and transfer of data. It encodes data in a format readable by both machines and humans. XML describes what the data is, while HTML determines how to display the data to the end user.

Read about XML »

What are the similarities between HTML and XML?

Both XML and HTML—along with other languages like LaTeX, SVG, Markdown, and SGML—belong to a family of programming languages called markup languages.

A markup language is a system for describing data to both humans and other software programs. It uses easy-to-read syntax that defines the data’s structure, type, attributes, relationships between parts, display, and meaning. 

As markup languages, HTML and XML have several similarities.

Syntax

Markup languages typically have a similar syntax, including tags and attributes.

Tags

Tags are denoted by symbols like brackets, commas, and periods. They provide structure and type to data elements. They define the beginning and end of each element of content. In XML and HTML, tags are enclosed within angle brackets, with each element between two opening and closing tags.

Attributes

Attributes provide more information about an element, such as an image URL. In HTML and XML, you define an element’s attributes inside the opening tag.

Well-defined structure

Both HTML and XML documents must adhere to the syntax rules of the given language for correct processing. A document that follows the rules is known as a well-formed document. A well-formed document requires the following:

  1. A single root element
  2. Closing (or self-closing) tags for all elements
  3. Correct nesting with tags enclosed in other tags
  4. Correct description of special characters, such as & for the & symbol

Developers use a text editor application or integrated development environment (IDE) to write and check the syntax.

Read about IDEs »

Usage

Developers typically don’t use the HTML or XML markup languages by themselves. These languages are combined with scripting languages to create dynamic webpages and applications. Dynamic applications change due to new incoming data.

In the case of HTML, application pages are dynamic through scripting languages that generate new HTML. For XML, scripting languages use new information to update parameters.

Platform independence

Platform independence is the ability of a language to work on different operating systems and platforms without requiring any modifications. Both XML and HTML are text-based and use simple syntax. This makes them easy to interpret by different software applications and operating systems. XML and HTML code works as is across browsers and different mobile platforms.

Main syntax differences: HTML vs. XML

The core difference between HTML and XML is in their tags. HTML has predefined tags that everyone has to use. You can’t make up your own tags while writing HTML. In contrast, XML uses custom tags you can define as a document creator.

Next, we talk more about how HTML and XML differ in their tags.

Predefined tags

In HTML, there are predefined tags. This means the tag itself comes from a set list defined by the HTML standard. The current HTML standard is HTML5. 

Here are examples of HTML5 predefined tags:

  • <header> is the tag for the header of document
  • <p> is the tag for a paragraph
  • <h1> to <h6> are tags for six levels of headings
  • <a> is the tag for a hyperlink
  • <img> is the tag for an image
  • <div> is the tag for a container element to group other elements
  • <body> is a tag that defines main content

Conversely, for XML, tags are extendable, which means they are custom-made for the document’s purpose. As a document creator, you would define the tags and attributes. They can be any combination of letters and numbers.

Typically, document creators use plain words that describe the data. You have to write an XML schema that defines the tags and attributes for document validation and shared understanding.

We give some examples of HTML and XML syntax in the following table.

HTML

XML

<p class="body_paragraph">This is a paragraph</p>

class= signifies that the element has a class attribute, body_paragraph, that can be used to apply styles.

<country language="English">Canada</country>

country signifies a country element. language signifies that the element has a language attribute, English.

<body>

<h1>This is a Heading</h1>

<p class="body_paragraph">This is a paragraph</p>

<div>

<h2>This is a subheading </h2>

<p>This is another paragraph</p>

</div>

</body>

<continent name="Europe">

<country language="English">

United Kingdom

<currency>GBP</currency>

</country>

<country language="German">

Germany

<currency>EUR</currency>

</country>

</continent>

Self-closing tags

In HTML, some elements can use self-closing tags—signified by a closing forward slash—due to a lack of content. A limited number of HTML tags can use self-closing tags.

In contrast, self-closing tags in XML can exist in any place where there is no content.

HTML

XML

<img src="my_image.jpg" alt="My image" />

<country name="United Kingdom" currency="GBP" />

Other key differences: HTML vs. XML

Despite their similarities, XML and HTML have several differences.

Objective

HTML is commonly known as the language of the web. HTML’s primary purpose is to display content, given in a text-based document, in a graphical form in the browser.

In contrast, XML allows different applications to exchange and store data and its structure in a way that is universally understood. The primary purpose of XML is to allow different types of applications, such as databases, to understand and use the same data and its structure. 

Typing

HTML uses dynamic typing, where attribute types are checked at runtime against the expected data type. For example, if an attribute is expected to be a number but is input as a string, it may cause an error or unexpected behavior of webpages at runtime. Dynamic typing allows for changes to webpages with new incoming data.

In contrast, XML uses static typing, where attribute types are predefined in an XML schema and checked before compiling or processing. Static typing leads to fewer errors but also less dynamic content.

Schema

Document type definitions (DTDs) or schemas provide a structure that can be validated and repeated for similar documents. They typically include information like this:

  • The HTML or XML version being used
  • Allowed elements and attributes
  • Rules for document structure and element relationships

In HTML, the DTD is a declaration included at the beginning of an HTML document.

In XML, the DTD is a separate file. The DTD is more important in XML because XML tags are defined by the document creator. The DTD contributes to the shared understanding of the tags between the data sender and receiver.

When to use HTML vs XML

HTML is a type of markup known as a presentation language. The name presentation language is due to the fact it is for display purposes. You use HTML to create webpages and client-side web applications. It’s typically combined with Cascading Style Sheets (CSS) for styling purposes and the JavaScript programming language for dynamic behaviors.

In contrast, you use XML for the exchange of data between two applications or systems. To understand the same format, the applications have shared XML schemas that define the content of an XML file.

While XML is still in wide use, JSON, another lightweight markup language for data exchange, is now more popular due to its fast parsing. You can read a comparison of JSON and XML to choose the best data exchange format for you.

How to use HTML and XML together

XML can be embedded in HTML and parsed with the JavaScript programming language to create webpages that are dynamic. Similarly, HTML can also be embedded in XML if necessary, using character data (CDATA) for plaintext. See the following examples.

XML in HTML

HTML in XML

<html>

  <head>

    <title>Embedded XML Page</title>

    <script type="text/xml">

      <data>

        <item>

          <name>Apple</name>

          <price>1.00</price>

        </item>

        <item>

          <name>Passionfruit</name>

          <price>2.00</price>

        </item>

      </data>

    </script>

  </head>

  <body>

    <h1>Dynamic Fruit Prices</h1>

    <div id="output"></div>

    <script>

      var xml = document.querySelector('script[type="text/xml"]').textContent;

      var parser = new DOMParser();

      var doc = parser.parseFromString(xml, "text/xml");

      var output = document.querySelector('#output');

      var items = doc.getElementsByTagName('item');

      for (var i = 0; i < items.length; i++) {

        var item = items[i];

        var name = item.getElementsByTagName('name')[0].textContent;

        var price = item.getElementsByTagName('price')[0].textContent;

        output.innerHTML += '<div><strong>' + name + '</strong>: ' + price + '</div>';

      }

    </script>

  </body>

</html>

<embeddedHTML>

    <title>HTML code embedded in XML</title>

    <description><![CDATA[

        <div>

            <h1>Embedded HTML header</h1>

            <p>Embedded HTML paragraph.</p>

        </div>

    ]]></description>

</embeddedHTML>

Extensible HyperText Markup Language (XHTML) is another markup language that combines both HTML and XML in its syntax.

Summary of key differences: HTML vs. XML

 

HTML

XML

What is it?

A markup language used primarily for displaying structured content in a browser.

A markup language used primarily for exchanging structured data between computer systems.

Year of release

1993.

1998.

Purpose

Presentation language.

Data exchange language.

Use when

Building client-side webpages or web apps.

Exchanging data between two systems (but check if JSON is a better format for you).

Tags

Predefined tags.

Extendible tags.

Typing

Dynamic.

Fixed when using an XML schema.

How can AWS support your HTML and XML requirements?

All Amazon Web Services (AWS) data integration services can process XML files. Here are two examples:

  • AWS Glue is a serverless data integration service that you can use to prepare data with an interactive, point-and-click visual interface without writing code. AWS Glue DataBrew can input all types of file formats, including XML.
  • Amazon Simple Queue Service (Amazon SQS) is a fully managed message queuing service that you can use to send, store, and receive messages between software components at any volume. Amazon SQS messages can contain up to 256 KB of text data, including XML, JSON, and unformatted data.

Similarly, AWS offers a broad set of tools and services to develop, deploy, and operate your applications at scale. For example, here are two services you can use:

  • With AWS Amplify, you can visually build a pixel-perfect UI. Connect your frontend UI to a cloud backend in a few clicks.
  • With Amazon Lightsail, you can use preconfigured development stacks to create custom applications and websites within just a few clicks.

Get started with your application development on AWS by creating an account today.

Next Steps with AWS

Learn how to get started with HTML 

Learn how to get started with XML