What is a key difference between JSON and XML?

The key difference highlighted in the answer is that JSON is more compact while XML is more verbose. This distinction is significant when considering how data is formatted and transmitted in web applications.

JSON (JavaScript Object Notation) has a lightweight and structured format that uses a straightforward syntax, which leads to smaller file sizes when compared to XML. Its structure, based on key-value pairs, allows for efficient data representation, making it ideal for data interchange between a server and a client, especially in web APIs. For instance, JSON requires fewer characters to represent the same amount of data, which allows for faster processing and transmission.

XML (eXtensible Markup Language), on the other hand, is designed with a focus on providing both clarity and extensibility. Its verbose nature comes from the requirement to define elements and attributes with opening and closing tags, leading to larger file sizes. This verbosity can make XML more readable for humans but can also result in increased bandwidth usage and slower processing times compared to JSON.

Understanding this difference is crucial for developers when choosing a data format for their applications, as it impacts performance and efficiency.