I have setup an Angular frontend and a .Net core backend. Both sites are running under self-signed SSL certificates because these are dev and I’m not purchasing trusted certificates. I could have used Let’s Encrypt to create a trusted cert, but I went for a longer life self-signed SSL instead.
See How to setup your SSL certificate… for information about that.
When I first loaded my Angular site it warned me about being an untrusted SSL cert so, in Chrome, I clicked the button to acknowledge that I’m aware it is not a trusted certificate, but proceed anyway. When I try to click a button in my Angular app that makes a call to my API, I get a “ERR_CERT_AUTHORITY_INVALID” error in my network traffic messages of my developer tools.
Just open your API url in your browser and acknowledge that you accept all the dangers of using using an untrusted SSL certificate, and load the API in your browser once.
Now your front end should be able to open the API without getting the warnings and work normally.