hi, https://medium.engineering/use-a-dev-domain-not-anymore-95219778e6fd

tl;dr don't use .dev for developement purposes - it's a gTLD owned by google and enforces https use since recently

That's not the problem since ".dev" domain are fully working on Google Chrome as I've got an SSL Self Signed Certificate on my localhost.

This problem is related to Firefox Developer Edition.

well, it is this problem since the .dev domain landed on the hsts preload list in firefox 59.0b7. if you have a self-signed certificate for your site, then you can import that through the "view certificates" button at the bottom of the firefox menu ≡ > options > privacy & security panel.

I've got this:

This personal certificate can’t be installed because you do not own the corresponding private key which was created when the certificate was requested.

And I've created the Certificate just today.

the other way i could think of, is temporarily downgrading to devedition below b7 (http://archive.mozilla.org/pub/devedition/releases/59.0b5/mac/), visiting the https domain and storing the exception this way & then upgrade the browser again.

due to https://tools.ietf.org/html/rfc6797#section-12.1 it isn't possible to add exceptions for hsts sites unfortunately.

OK Downgrading my Firefox to 59.0b5 worked: http://archive.mozilla.org/pub/devedition/releases/59.0b5/mac/

Which of course is just a temporary solution. Hopefully this will be solved soon!

the workflow would be: downgrade, access the https version of your local site, store the exception & upgrade again

Miguel said

And I've created the Certificate just today.

What certificate issued the certificate you created? You'll have to import that into the "Authorities" section of the certificate manager (and trust it for websites).