Is XML a dated markup language compared to JSON?

The answer is: It depends. While many projects have benefitted with the switch to JSON, the reality is that XML is here to stay, at least in some applications.

Read on for our take on the pros and cons of XML vs JSON

Cons

1. Simplicity and Verbosity: XML is more verbose than JSON. The tags in XML add extra information that often isn't necessary for data representation. JSON, on the other hand, uses a more compact format, which makes it easier to read and write by both humans and machines.

2. Data Structure: JSON's data structures – arrays and objects – align more closely with the data structures in many popular programming languages. This makes parsing and generating JSON more straightforward.

3. Metadata vs. Data: XML mixes both data and metadata (in the form of tags), while JSON is purely about data. This distinction can make JSON easier to work with since you're only dealing with the data itself.

4. Popularity in Web Development: JSON has become the de facto standard for many web APIs. Its compatibility with JavaScript – JSON stands for "JavaScript Object Notation" after all – has made it the preferred choice for many web developers.

5. Performance: Given its verbosity, XML can result in larger payloads when sending data across the web, which can impact performance. Parsing XML can also be slower compared to JSON.

6. Flexibility: While XML's flexibility in allowing attributes, mixed content, and other features can be seen as an advantage, it can also lead to complexities. JSON's simpler structure avoids these complexities.

Pros

1. Document Markup: XML was designed as a markup language for documents, and it excels in scenarios where data isn't strictly structured, like mixed content in texts.

2. Data Description: XML's verbose nature can be an advantage when the goal is to describe data in a self-documenting way. XML namespaces, for instance, can help in avoiding naming conflicts.

3. Mature Tooling: Given its age, XML has a mature ecosystem with various tools, schemas, and transformation languages (like XSLT).

4. Standardization: Many industries and systems still use XML-based standards, especially in contexts where the standard was developed before JSON became popular.

In summary, while XML may seem dated in the context of modern web applications, it still has specific scenarios where it is the preferred choice. However, for many new projects, especially those focused on web technologies, JSON is often the more modern and popular choice.