Making sure the domains listed in this article are allowed by your firewall or other software ensures that Firefox works correctly.

Update Service (Firefox and GMP)

https://aus5.mozilla.org

Remote Settings

https://firefox.settings.services.mozilla.com https://firefox-settings-attachments.cdn.mozilla.net https://content-signature-2.cdn.mozilla.net

Download locations for Firefox

https://download.mozilla.org https://download.cdn.mozilla.net https://archive.mozilla.org https://ftp.mozilla.org

Telemetry

https://incoming.telemetry.mozilla.org

Captive Portal Detection

http://detectportal.firefox.com

Safe Browsing

https://safebrowsing.googleapis.com

Pocket

https://img-getpocket.cdn.mozilla.net https://getpocket.cdn.mozilla.net

Mozilla accounts

https://accounts.firefox.com https://profile.accounts.firefox.com/

Sync

https://token.services.mozilla.com https://sync-1-us-west1-g.sync.services.mozilla.com

Tracking Protection (What exactly does it do)?

https://tracking-protection.cdn.mozilla.net

Location Services

https://location.services.mozilla.com

OpenH264 Video Codec Download

http://ciscobinary.openh264.org

Widevine Content Decryption Module Download

https://redirector.gvt1.com https://clients2.googleusercontent.com

DNS over HTTPS

https://mozilla.cloudflare-dns.com https://dns.shaw.ca https://doh.xfinity.com https://firefox.dns.nextdns.io https://private.canadianshield.cira.ca

Extension Update

https://versioncheck.addons.mozilla.org/

Extension Metadata for about:addons

https://services.addons.mozilla.org/

New Tab Sponsored Tiles

https://contile-images.services.mozilla.com

New Tab Sponsored Stories

https://spocs.getpocket.com