While both are Application Programming Interfaces (APIs) operating over the HTTP protocol, SOAP (Simple Object Access Protocol) is a standards-based web services access protocol that’s been around for quite a while— it relies exclusively on XML for messaging services. It has much tighter security than REST and features success/retry logic for reliable messaging. It also features built-in ACID compliance and is language, platform, and transport independent. REST (Representational State Transfer) is truly a “web services'' API, using the JSON data format. REST APIs are usually easier to use and more flexible than SOAP, with a gentler learning curve. They tend to be faster, more efficient, and closer to other web technologies' design philosophy.