XML format
SOAP envelope
The message envelope for SOAP web services, still the backbone of banking, logistics and telecom integrations.
A SOAP message is an <Envelope> with an optional <Header> and a mandatory <Body>. The version is carried by the envelope namespace URI rather than an attribute, so URI comparison is the only correct way to detect it.
Errors are in-band: a fault is a normal <Body> child, often returned with an HTTP 500. That means a failed SOAP call and a successful one are the same shape at the transport layer, and only the payload distinguishes them.
Constraints that bite
- SOAP 1.1 and 1.2 use different envelope namespaces and different fault structures.
- Exactly one <Body>; <Header> is optional but must come first if present.
- A fault is a Body child, not a transport error — HTTP 500 with a valid envelope is normal.
- Prefixes vary wildly (soap:, soapenv:, SOAP-ENV:, s:) — always match on the namespace URI.
- Headers marked mustUnderstand="1" must be rejected if unrecognised, not ignored.
- Root element
<Envelope>- Media type
application/soap+xml- Extensions
.xml- Namespaces
http://schemas.xmlsoap.org/soap/envelope/http://www.w3.org/2003/05/soap-envelope
- XMLDir label
soap
Specification: SOAP 1.2 Part 1
A minimal valid document
Every example on this site is checked against the same parser the workspace uses, so what you see below is known to be well-formed.
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetOrder xmlns="https://example.com/orders">
<OrderId>10024</OrderId>
</GetOrder>
</soap:Body>
</soap:Envelope>Namespaces you will meet
SOAP 1.1 envelope
http://schemas.xmlsoap.org/soap/envelope/The SOAP 1.1 envelope namespace. Distinct from SOAP 1.2 — the version is encoded in the URI.
SOAP 1.2 envelope
http://www.w3.org/2003/05/soap-envelopeThe SOAP 1.2 envelope namespace, and the reason a 1.1 endpoint rejects a 1.2 message outright.
WSDL 1.1
http://schemas.xmlsoap.org/wsdl/The service-description namespace for SOAP web services. Still the version almost every deployed WSDL uses.
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