What is the difference between REST and SOAP, and when would you choose each for a Salesforce integration?

REST (Representational State Transfer) is stateless — every request contains all information needed to process it. It uses standard HTTP verbs (GET, POST, PUT, PATCH, DELETE) and typically exchanges JSON, making it lightweight and easy to consume by modern web and mobile clients. SOAP (Simple Object Access Protocol) is stateful-capable, uses XML exclusively, and relies on a WSDL (Web Services Description Language) contract to define the interface.

Choose REST when: you need lightweight, high-performance integrations with web/mobile apps, the external system supports JSON, or you want simple URL-based endpoints. Choose SOAP when: you need built-in WS-Security, ACID transactions, or must integrate with legacy enterprise systems that expose only WSDL-based services. Salesforce exposes both: the REST API (JSON/XML) and the SOAP API (WSDL-based). Most modern integrations prefer REST.