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I wanted to give Firefox for Android a try (I'm a long-time Chrome user), but after installing it from the Play Store, I discovered it refuses to load any website, always showing this security warning that cannot be ignored:

This website requires a secure connection

This happens on all sites and only on Firefox for Android, the same sites load correctly in Chrome and also load correctly in Firefox running on a Windows computer that is on the same network as my Android device.

Any clues as to why this is happening? I'm running Firefox 105.1.0 on Android 12.

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  • Check the system date. If it is wrong HTTPS connections will fail because the used certificate is not yet or no longer valid.
    – Robert
    Sep 24, 2022 at 10:46
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    AFAIK, Firefox uses its own certificate store, not the Android native certificate store. What happens if you try setting security.enterprise_roots.enabled to true on about:config?
    – Andrew T.
    Sep 24, 2022 at 13:10
  • @Robert: thanks but date was ok, problem was a different one, check my answer for details
    – Master_T
    Sep 24, 2022 at 16:17
  • @AndrewT. Thanks for the comment, it pointed me in the right direction to solve the issue, see my answer for details
    – Master_T
    Sep 24, 2022 at 16:17
  • @Master_T So your device is rooted (-> not mentioned in question)? because otherwise you could not have installed a root CA certificate.
    – Robert
    Sep 24, 2022 at 16:21

1 Answer 1

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After doing more digging, it seems the problem was my adblocker (AdGuard). It uses a locally installed CA certificate in order to filter HTTPS traffic. By default Firefox ignores local CA certificates, it has its own list of trusted CAs. Quite dumb in my opinion, but luckily local CA certificates can be enabled by following this guide:

https://kb.adguard.com/en/android/solving-problems/firefox-certificates

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  • Instead of using a VPN app you can avoid issues like this by setting your private DNS to their server. adguard-dns.io/en/public-dns.html
    – Tanath
    Nov 13, 2022 at 0:41
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    @Tanath: that is not nearly as effective though, a lot more ads get through if you only use DNS filtering...
    – Master_T
    Nov 14, 2022 at 14:50
  • It's DNS filtering either way, and my experience has barely any ads getting through. It's even the same provider so the filters should be the same.
    – Tanath
    Dec 10, 2022 at 3:33

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