# If you are uploading file in params, multipart will used as content-type automatically HTTParty.post( 'http://localhost:3000/user', body: { name: 'Foo Bar', email: 'example@email.com', avatar: File.open('/full/path/to/avatar.jpg') } ) # However, you can force it yourself HTTParty.post( 'http://localhost:3000/user', multipart: true, body: { name: 'Foo Bar', email: 'example@email.com' } )