What is the difference between REST and SOAP?

REST is an architectural style built on standard HTTP, using lightweight JSON/XML payloads and standard HTTP verbs/status codes — simple, cacheable, and the default choice for most modern web/mobile APIs. SOAP is a strict, XML-based protocol with a formal contract (WSDL), built-in security/transaction standards (WS-Security, WS-AtomicTransaction), and works over multiple transports beyond HTTP — it's heavier but still used in enterprise/financial systems that need those formal guarantees.