Mock API Builder supports REST, GraphQL, gRPC, and SOAP. Each project uses exactly one protocol — pick the one that matches the API you are mocking.
Choose the protocol your client or backend contract already uses. You do not mix protocols inside a single project.
HTTP resources with paths, methods, and JSON bodies. Define fields manually, paste JSON, or import OpenAPI/Swagger.
Best for: web and mobile apps that call REST APIs.
Try it liveImport a GraphQL SDL. Queries and mutations become mock operations served at a single endpoint.
Best for: apps that already speak GraphQL.
Import a .proto file. Services and RPC methods become mock endpoints (unary and streaming).
Best for: microservice and mobile clients using protobuf.
Import a WSDL. Operations are mocked with SOAP envelope XML responses (SOAP 1.1 and 1.2 clients).
Best for: enterprise integrations that still use SOAP.
On the create-project form, REST is the default. To use another protocol:
.proto, or WSDL.You can also create a blank project and let the first import lock the protocol. Once any endpoint exists, the project is locked to that protocol.
Each project uses exactly one protocol. That rule is enforced on the server:
Need both REST and GraphQL? Create two projects — one per protocol — and point each client at the matching base URL.
Each protocol has its own request path. Using the wrong path is a common mistake when switching protocols.
Example: /api/grpc/users.v1.UserService/ListUsers
The project page opens a protocol-aware tester:
/api/graphql/{slug}application/grpc+json)/api/soap/{slug}See Testing & Debugging APIs for details.
Prefer a hands-on demo? Each protocol has a sample page with a sample schema and request: