> some.site.example.com has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site. > > The issue is most likely with the website, and there is nothing you can do to resolve it. > > If you are on a corporate network or using antivirus software, you can reach out to the support teams for assistance. You can also notify the website’s administrator about the problem. This is super frustrating. How to use Firefox for development purposes? There should be an option to add exceptions. I even went to settings and added an exception manually to no avail. I'm going often through pain to use firefox for everything but then there must be a reasonable way to achieve the goals. Please tell me there is a way to workaround this easily without compromising security of other sites that are being visited. P.S. I can open same site with adding an exception on chrome. Related question but with an answer that doesn't make sense in my case: https://support.mozilla.org/en-US/questions/1324365