How do I implement akka-http-cors correctly to be able to allow access from any origin (domain, in my case localhost:3000) to a Https Server (Scala/Akka)? Based on the akka-http-cors documentation should defaultSettings do the job, but I am still doing something wrong: Google Chrome Error: Firefox Error: akka-http-core: https://github.com/lomigmegard/akka-http-cors#configuration Any help is highly appreciated! Answer The problem in my case