JSON vs. XML: What’s The Difference?

When an application exchanges data between two computers, it often uses JavaScript Object Notation (JSON) or eXtensible Markup Language (XML). JSON has become more popular than XML in recent years, with Google Trends showing search interest in JSON overtaking XML in 2015 [1]. The history of the two languages is complex, intertwined, and far from finished, especially since both languages do the same thing: exchange data. Still, each language has advantages over the other, JSON, for its simplicity over XML's complexity. 

Explore the interesting history, various use cases, and fervent defenders of both JSON and XML so that you can decide on an exchange format that best suits your workflow. 

A brief history of XML and JSON

In the early days of developing the web, the lack of HTML protocols and standards led to a divergence in HTML usage between Netscape and Microsoft, two of the era’s popular web browser applications. This made it challenging for developers to create applications that both browsers could support. XML emerged as a solution to prevent further web fragmentation and facilitate data interchange between applications. While not fully solving the problem, XML usage ushered in a way to store, exchange, and validate data that any application could read. 

One of the primary issues with Web 1.0 was that the entire HTML page was rendered per user, which required a lot of server resources and architecture. With the development of Java as a back-end object-oriented programming language, web pages became more complex, and a system was needed to suit the complexity. This led to the integration of Asynchronous JavaScript and XML (AJAX), which allowed data to flow to a webpage without reloading it.

While AJAX would solve the problem, before its full development for all web browsers, David Crockford and Chip Morningstar utilized the JavaScript format to deliver data using HTML, allowing data to flow without reloading the page. While the approach of using JavaScript to send data was not novel, Crockford and Morningstar ratified it by naming it JSON. Since AJAX already used JavaScript, replacing XML with JSON became a popular approach for application developers. 

What is XML?

XML is a markup language that uses tags to define data structure. Wrapping data in XML tags allows any application or operating system to process that data. When writing an XML document, you create tags that best describe your data, unlike HTML, which uses pre-defined tags like <h1>, <p>, etc. to define Heading 1 and the paragraphs of a webpage. Say you have a store and share user data like name, age, email, and phone number. The XML would look like this:

<?xml version="1.0"?>

<user>

<name>Johnny Appleseed</name>

<age>32</age>

<email<johnny@applseed.com</email>

<updated>yes</updated>

</user>

XML schema

XML schema, which is basically a file of rules governing XML data files, provides the structure for an XML document. It is also in the structure of an XML file, but uses .xsd instead of .xml to differentiate itself from the data document. Schema documents give the structure so that data validation for an XML document can occur. The file must contain the proper structure and have valid syntax before it is validated and processed by an application. For the user example, a schema would look like this:

<xsd:element name="user">

<xsd:complexType>

 <xsd:sequence>

 <xsd:element name="name" type="xsd:string"/>

 <xsd:element name="age" type="xsd:positiveInteger"/>

 <xsd:element name="email" type="xsd:string"/>

 <xsd:element name="updated" type="xsd:boolean"/> 

 </xsd:sequence>

 </xsd:complexType>

</xsd:element>

Combining the XML data document, the XML schema document, and an Extensible Stylesheet Language Transformation (XSLT), called a transform, allows you to transfer data from one system to another and make up the system's XML uses for data transformation. 

Advantages of XML

XML has many advantages when it comes to communicating data across formats, databases, and businesses by putting data into a form that’s universally recognizable. Some additional benefits of XML for interchangeable communication include:

• The strict schema provides data integrity between systems, ensuring that the data in the file is valid. 

• The structure of XML makes it useful for creating technical documentation. Its tagging system gives you the ability to define steps while still being able to give alternative steps in a procedure. 

• XML is an internationally recognized standard and is completely open-source; all you need to write and read XML is a text editor, making it a flexible format for any business. 

• Once you have your data or content in an XML document, you can use an XSLT to transform it into any format you need, like creating both a web application and a mobile application, without having to duplicate information. 

Disadvantages of XML

The development and further implementation of JSON by developers addressed many of XML's disadvantages, most notably its verbose syntax and slow read speeds. Other disadvantages of XML include:

• The need to use a dedicated XML parser to parse XML

• The verbosity of XML is off-putting because its tag structure requires the closing of the angle brackets <> for every opening and closing tag, for example, <tag>This is a tag</tag>. When put into an entire XML document, this can make the structure difficult for humans to decipher. 

What is JSON?

Like XML, JSON is a data exchange format that stores and sends data between applications and programming languages. JSON stores data using key-value pairs using curly braces “{}” with each value separated by a comma. Storing the same information as in the XML example, but with JSON would look like:

“user”: [ { “name”: “Johnny Appleseed”, “age”: “32”, “email”: “johnny@appleseed.com”, “updated”: “yes”, } ]

What is JSON used for?

JSON has many applications beyond sending data in a format that both humans and machines can read. Some of those applications include: 

• Creating temporary data files, such as a user-submitted forum. 

• Configure database credentials and log paths for applications to connect to databases across various platforms and systems. 

• Storing user profiles in a database with each attribute specifically targeting that user. 

• Easily put information like product catalogs into one JSON file for faster speed compared to a traditional relational database for products with multiple attributes. 

Advantages of JSON

JSON’s syntax is lightweight, platform-independent, and readable by humans, making it a popular choice for developers. Some of its advantages over XML include:

• JSON can create JSON document databases, which are nonrelational databases that store JSON documents and allow you to query them as in a relational SQL database. 

• JSON document databases are flexible and can easily be updated and accessed.

• JSON syntax is simpler, flexible, readable, and can be parsed via a JavaScript function instead of a separate parser. 

Disadvantages of JSON

JSON improves on many of the disadvantages of XML, like the need for separate parsers and verbose formatting, but does have a few potential drawbacks. While its simplicity makes it popular with developers, JSON has a couple of disadvantages, including the following:

• JSON is not able to represent as complex a data structure as XML, leading to errors in the higher layers of an application in something like an enterprise application with varying architecture and complexity. 

• JSON potentially contains some serious security risks in which malicious actors can insert JavaScript into a string. If other JavaScript code is in a previous statement, then the browser will automatically run the Trojan Horse code when it runs the JavaScript, potentially allowing access to the user's computer.

Other things to consider with JSON vs. XML

JSON and XML both interchange data between applications. However, newer developments in JSON’s lightweight syntax and speed make it a more efficient format for smaller programs. Many developers use JSON because of its similarity to JavaScript syntax, making it efficient to store data from a JavaScript application. Data from a 2024 Developer Survey from Stack Overflow reveals that 62.30 percent of professional developers reported using JavaScript extensively over the past year [2].

While JSON has many advantages over XML for modern application workflows, many aspects of XML’s structure, schema, and validation make it a more effective option for complex enterprise usage. XML represents more than just data interchange for an application; it also holds libraries and frameworks. 

In short, simple applications benefit greatly from the speed and simplicity of JSON. However, XML's more complex structure allows it to represent not just data, but entire libraries and configurations without relying on external tools—something JSON typically requires. This makes XML a better fit for enterprise-level applications.

Get started in web development on Coursera

JSON and XML are powerful data structures for transferring information from one system to another. Continue learning about web development and building in-demand skills with online programs on Coursera. For example, consider the IBM Back-end JavaScript Developer Professional Certificate, during which you can become more familiar with using JavaScript to develop back-end applications, implement Agile methodologies, and deploy applications using tools like Docker or Kubernetes. Another option, the Microsoft Full-Stack Developer Professional Certificate, can help you build foundational knowledge in object-oriented programming, continuous integration and continuous deployment (CI/CD), and optimizing system performance and security.