SOAP

ELI5 - The Vibe Check

SOAP is the older, stricter, more ceremonial way APIs used to talk to each other, wrapping every request in a formal XML envelope with a rigid contract defining exactly what's allowed. It's the API equivalent of writing a business letter with a required salutation and closing, versus REST's more casual just-send-me-some-JSON-we'll-figure-it-out approach.

Real Talk

SOAP (Simple Object Access Protocol) is an XML-based messaging protocol for exchanging structured information between services, defined by a strict specification and typically paired with a WSDL (Web Services Description Language) contract that formally describes available operations and message formats. It predates REST and remains common in enterprise, banking, and government systems that value its built-in standards for security and transactional reliability over REST's simplicity and flexibility.

Show Me The Code

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
  <soap:Body>
    <GetPrice xmlns="https://example.com/prices">
      <ItemId>42</ItemId>
    </GetPrice>
  </soap:Body>
</soap:Envelope>

When You'll Hear This

"The bank's legacy API is still SOAP, we had to write an XML client just for this integration." / "WSDL generated the client code for us, at least SOAP has that going for it."