In which format does SOAP primarily use for messaging?

SOAP (Simple Object Access Protocol) primarily uses XML for messaging because XML provides a flexible and structured way to transmit data over a network. This allows for a consistent approach to communication that can be easily understood by different systems, irrespective of their underlying technology.

XML offers important features such as extensibility, which means that developers can define their own tags and structure them in a way that makes sense for their business needs. Additionally, the hierarchical nature of XML allows for complex data to be represented effectively, making it suitable for the detailed information conveyed in SOAP messages.

In contrast, JSON, while popular for data interchange, is not the primary format used by SOAP. HTML and CSV also do not meet the requirements of a messaging protocol like SOAP, which requires a structured format that can encapsulate both data and the necessary metadata for transaction processing. Therefore, XML is the correct and established format that aligns with the specifications of SOAP messaging.