WireMock : Free and Open Source tool for building mock APIs. Create stable development environments, isolate yourself from flakey 3rd parties and simulate APIs t...
Postal : Postal is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready f...
mountebank : mountebank is the first open source tool to provide cross-platform, multi-protocol test doubles over the wire. Simply point your application under tes...
Matrix : Matrix is an open standard for decentralised communication, providing simple HTTP APIs and open source reference implementations for securely distribu...
gRPC : gRPC is a modern, open source remote procedure call (RPC) framework that can run anywhere. It enables client and server applications to communicate tr...
Mockoon is the easiest and quickest way to design and run mock APIs. No remote deployment, no account required, free and open-source.