XML vs HTML: Differences and similarities

Markup code, or markup language, is basically a set of words and symbols created by the computer industry with the goal of helping to process, organize, and present information, as well as to inform the computer on how to interpret a document. 

As opposed to other programming languages, markup languages are both user-friendly and machine-friendly. Generally, they include standard words in a syntactical way that allows them to be easily understood by the reader. Although a number of different markup languages exist, HTML and XML are two of the most commonly used markup languages. 

In recent times, HTML and XML have become two of the most popular languages used across the internet. Due to their wide range of applications, advantages, and disadvantages, these languages can be used in a variety of different scenarios. Here, we will compare two of the most markup languages in various aspects.

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What is XML?

The Extensible Markup Language (XML), also known as the XML Schema, is a markup language for describing, formatting, transmitting, and reconstructing arbitrary data in a variety of formats. It outlines the rules for encoding documents in a way that makes them both machine-readable and human-readable. In terms of its dynamic nature, it serves as a means of transporting data, not for displaying it.

XML emphasizes simplicity, generality, as well as a degree of flexibility to operate across the Internet. While the XML is centered on documents, the language can also be used to represent any arbitrary data structure, including those used for web services. Users have the freedom to design their own tags in XML — they are self-descriptive.

Features of XML

• As XML stores data in plain text format, it simplifies data storage. This makes retrieval easier than in databases.
• When it comes to the transport of data, XML files are great, especially for applications that are not compatible with rendering other data formats. 
• The XML format is compatible with many reading devices, making it accessible to those who are blind or have other disabilities.
• The XML language is extensible. Users can create self-descriptive tags in any language depending on the application requirements.
• There are no predefined tags in XML. It is important to define your customized tags.

What is HMTL?

HyperText Markup Language (HTML) is a standard language for web-based documents. It consists of a series of elements that wrap and enclose content, causing it to behave or appear in a particular way.

Using the enclosing tags, you can hyperlink words or images, italicize words, make fonts bigger or smaller, among other abilities. Aided by technologies such as Cascading Style Sheets (CSS) and scripting languages like JavaScript, this process can be more easily accomplished. An enclosing tag can hyperlink a word or image to another, italicize words or make the font bigger or smaller.

It is used to annotate (note for the computer) text so a machine can better understand it and manipulate the text. Furthermore, website designers can use HTML to create ordering forms, reservations, and search forms. The HTML coding language, therefore, is the cornerstone of building your brand and running your online subscription-based business. 

Features of HTML

• Besides being a simple, easy language, it supports authoring web pages and is easy to learn.
• Codes can be modified and are easily understood by everyone. 
• HTML contains many tags that can be used to create web pages.
• This tool allows the creation of web pages with the content of the user’s choice.
• Moreover, it provides hyperlinks to other pages, which makes browsing much easier.
• The HTML language is independent of the operating system (OS). It is compatible with Windows, Mac, and Linux.
• Pages can be embellished with graphics, sounds and videos, which makes them very attractive. 
• It is easily compatible with scripting and styling languages such as CSS and JavaScript, enabling dynamic functionality.
• There is enough support to embed multimedia in documents.
• It is flexible enough to support hypertext links if necessary.

XML vs. HTML

Although both HTML and XML are markup languages, they differ significantly in many ways. Both have many advantages and disadvantages that can also be taken into account when making decisions. These are some of the most significant differences between the two:

1. Objective

By its very nature, XML is designed for the purpose of transporting and storing information.

By contrast, HTML is used to enhance the appearance of text and data.

2. Tags

As part of XML, the user has the option of creating tags. This allows users to create tags in any language they desire.

Tags are predefined in HTML. A user can use the tags to create web pages based on their needs.

3. Nature

Since XML is used for data transport, it is dynamic in nature.

Because HTML is primarily used to display data, it is static in nature.

4. Language Type

Since XML is case-sensitive, it’s important to keep the upper and lower cases in mind when writing code.

Since HTML is not case-sensitive, upper and lower case are not important.

5. Coding Errors

XML does not give the final result if there is an error in the code.

Small coding errors can be ignored in HTML and the outcome can still be achieved.

6. Document size

The document size can be large in XML.

HTML does not support lengthy documents. A best-formatted output can be achieved by simply adding the syntax.

7. Eng of tags

A well-formed XML document must have a closing tag.

A closing tag isn’t always needed in HTML. While the <HTML> tag must be paired with a </HTML> tag, the <br> tag does not require a </br> tag.

8. Whitespaces

In XML, whitespaces are preserved — you may use them in your code.

The HTML language does not preserve whitespaces, so you cannot use them in your code.

9. Nesting

In XML, nesting needs to be done appropriately.

Nesting does not affect HTML code in any way.

10. Drivers

As XML is content-driven, it does not have many formatting options.

HTML, however, is presentation-driven. The appearance of the text is extremely important.

11. Object Support

XML objects are expressed using conventions, mainly attributes and elements.

The HTML language supports native objects.

12. Null Support

XML instance documents must use xsi:nil on elements and the corresponding namespace must also be imported.

The HTML language recognizes the null value natively.

13. Formatting Decisions

In XML, mapping application types to XML elements and attributes takes more time and effort.

Direct mapping is provided for application data in HTML.

14. Document Size

A document in XML usually has a large size, especially when it uses an element-centric approach to formatting.

HTML has a brief syntax and produces formatted text.

15. Parsing in JavaScript

XML requires a DOM implementation and JavaScript code to map the text into objects.

To parse text in HTML, there is no need to write any extra application code. This can be accomplished using JavaScript’s eval function.

16. Learning Curve

It is very difficult to learn XML because it entails learning technologies such as DOM, XPath, and XML Schema.

Developers are familiar with HTML as it is a simple technology stack.

Conclusion

XML and HTML are both markup languages that deal with data and can be used together. They both utilize Standard Generalized Markup Language (SGML) and respond to browser requests directly or using AJAX. The HTML code is responsible for displaying the data, whereas the XML code is responsible for storing and transferring the data. Even though both languages are markup languages, their working methods differ greatly. 

HTML and XML form the structural foundation of every website or application, so learning them is crucial. While HTML is a simple predefined language, XML is a standard language used to define other languages. The importance of learning both HTML and XML cannot be overstated, since they are the foundations of all websites and applications, serving as the structural and integral elements. 

Shivam Bhatele is a software developer.