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...
httpbin.org : A simple HTTP Request & Response Service.
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...
Cool QL Cool : CoolQLCool (CQC) is an open source GraphQL server that allows you to turn websites into GraphQL APIs.
Mockoon is the easiest and quickest way to design and run mock APIs. No remote deployment, no account required, free and open-source.