This tutorial will help you enable a security on Firefox web browser on your Ubuntu 24.04 "Noble Numbat" to prevent your web browsing from being eavesdropped or blocked or redirected by anyone else. This is called "DNS over HTTPS" or shortened "DoH". More importantly, you can also easily block adult websites so it will be safer for your children and family to use your Ubuntu computer. Now let's start it out!

1. Run Firefox

2. Click triple line button to the right > Settings

3. Find DNS

4. Found DNS over HTTPS Settings

5. Select "Increased Protection" option

6. Leave it unchanged or select one option among other options:

- Cloudflare

- Nextdns

- Custom

See picture below:

7. If you want a custom DoH provider other than Cloudflare or Nextdns above, select "Custom" option then fill in one of URLs below. Just copy and paste it! Remember that the ones with "Family" words are useful to block adult websites.

- Quad9: https://dns.quad9.net/dns-query

- OpenDNS Regular: https://doh.opendns.com

- OpenDNS Family: https://doh.familyshield.opendns.com

- Adguard Regular: https://dns.adguard.com/dns-query

- Adguard Family: https://dns-family.adguard.com/dns-query

See picture below:

8. Configuration finished. 

If you found a problem such as failed to browse any website, you may need to quit Firefox and start it again. Now you can browse safely. Happy browsing with your family!

 9. To disable DoH or going back to normal:

Go to DNS settings and select "Default Protection" and you will revert back to use your default DNS from your internet service provider (ISP).

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References 

DNS Over HTTPS Explanation (Wikipedia)

Recommended DNS Services (Privacy Guides Community) 

AdGuard Public DNS Service

OpenDNS Public DNS Service 

Quad9 Public DNS Service

You might have been familiar with being blocked to visit Wikipedia or Reddit or such sites in your country. That means your network, DNS path in particular, is not secure. If you can make it secure, you can visit that sites just like other sites normally. You can do that with the previous DNSCrypt Guide or fortunately these days it is even more simpler, enable Dns Over Https (DoH) on your web browser. This simple guide is applicable to Ubuntu, Mint, Trisquel (Abrowser), PureOS (PureBrowser), and any other GNU/Linux systems. Now let's go secure!

(Visiting Reddit.com/Ubuntu social media discussion with DoH)

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