Some people are concerned about the connections Firefox makes to the Internet, especially when those connections are made for no apparent reason (see Mozilla's Firefox Browser Privacy Notice for additional information). This article explains various reasons why Firefox may make a connection to the Internet and how you can stop it from doing so, if you wish.
Automatic updates and Security Auto-update checkingWarning: Disabling update checking is not recommended and will leave you open to security vulnerabilities that get fixed in newer versions.
Firefox occasionally checks to see if any updates are available for itself and for your search engines. The ability to disable Firefox update checking was removed in Firefox 63. Advanced users and IT administrators can use a policy to disable Firefox update checks. See Manage Firefox updates.
Firefox also checks to see if any updates are available for your add-ons (extensions, themes). To disable this check:
Warning: Disabling add-on update checking is not recommended and leaves you open to security vulnerabilities that get fixed in newer versions.
Warning: Disabling the blocklist is not recommended, as it may result in you using untrustworthy add-ons, revoked certificates or unstable graphics drivers.
Firefox may be updating its blocklist, which is used to block malicious extensions, vulnerable plugins, revoked certificates and graphics drivers known to cause crashes. For more information, see Add-ons Blocking Process (Firefox Extension Workshop), Blocklisting/Graphics (MozillaWiki), Revoking Intermediate Certificates: Introducing OneCRL (Mozilla Security Blog) and the Why does Mozilla disable some add-ons from running in Firefox? article. To disable this feature:
Warning: Disabling phishing and malware protection is not recommended, as it will leave you vulnerable to malicious or unwanted downloads and to untrustworthy websites that try to steal your financial information and/or your identity.
Phishing, unwanted software and malware protection lists may be updating. To turn this off:
In addition, when you download an application file, Firefox will verify its signature. If it is signed, Firefox then compares the signature with a list of known safe publishers. For files that are not identified by the lists as “safe” (allowed) or as “malware” (blocked), Firefox asks Google’s Safe Browsing service if the software is safe by sending it some of the download’s metadata. To turn off this part of malware protection:
The tracking protection list may be updating itself. To turn this off:
When you visit a secure website (i.e. “https”), Firefox will validate the website's certificate. This may involve communicating with a third-party status provider specified by the certificate over a protocol named OCSP to confirm that the certificate is still valid. To turn this off:
Firefox Monitor warns you if your online accounts were involved in a known data breach. For more information, see Firefox Password Manager - Alerts for breached websites.
To get the latest login breach information and more, Firefox connects to firefox.settings.services.mozilla.com
Firefox will prefetch certain links if any of the websites you are viewing uses the special prefetch-link tag. For more information, please see the Link Prefetching FAQ. To disable Link prefetching:
In order to reduce latency, Firefox will proactively perform domain name resolution on links that the user may choose to follow as well as URLs for items referenced by elements in a web page. For more information, please see the DNS Prefetching blog post. To disable DNS prefetching:
To improve the loading speed, Firefox will open predictive connections to sites when the user hovers their mouse over thumbnails on the New Tab page or the user starts to search in the Search Bar, or in the search field on the Home or the New Tab page. In case the user follows through with the action, the page can begin loading faster since some of the work was already started in advance. To disable this feature:
Each time the Add-ons manager is opened, Firefox prefetches a list of add-ons to improve responsiveness of the panel. This connection is not made if the add-ons manager is not opened.
User-invoked content Home page loadingTo set your home page to something that doesn't generate connections to the Internet:
An extension you have installed may be making a connection to a website that it relies on. For example, a connection to a website to synchronize your bookmarks, a connection to a website to update a list of sites to block, etc. Or it is possible an extension could be changing the expected behavior of Firefox in other ways. For example, FasterFox extension has an option to prefetch all links. To disable or remove your extensions, see Disable or remove Add-ons.
Downloads restartedWhen you start Firefox, any interrupted downloads from your previous browsing session may be automatically resumed.
When you add a custom search plugin that doesn't come with an included icon, Firefox might look up the icon at a remote address that is specified in the search plugin once and cache it for future use.
Firefox SyncIf you're using Firefox Sync, it will establish regular connections in order to synchronize your data to Mozilla's Sync servers and across your connected devices. In order to choose what data gets synchronized or to disconnect from Sync, see How do I choose what information to sync on Firefox?
Mozilla content Contextual feature recommendations and other notificationsFirefox may make feature recommendations specific to a type of website you're on or relevant to a current task. You can disable connections by opting out of all Firefox recommendations via Firefox settings. See Recommendations from Firefox for details.
Experiments or studiesIn order to set the right default search engine for your location, Firefox will perform a geolocation lookup once by contacting Mozilla's servers and store the country-level result locally. This connection happens on the first start of Firefox – in case you want to prohibit that, you will have to preconfigure the browser and set the browser.search.geoip.url preference to a blank string.
“What's new” pageAfter a browser update, Firefox might show an additional tab next to your usual homepage to offer more information on changes or new features included in the update. To disable this page from being shown:
The Add-ons manager displays information about each add-on you have installed and provides personalized recommendations in the panel. To keep this data updated, Firefox will request information from the Mozilla Add-ons gallery once a day (for more information, see this blog post). To disable these updates:
Firefox can submit certain diagnostics data, including Telemetry and Crash Reports data to Mozilla, to provide information that helps improve the browser. You can disable sharing of this data in Firefox Settings . To disable the sharing of this data:
In addition, Mozilla will ask a small sample of users to rate their experience with Firefox to get a better insight into the sentiment about the browser. For more information about this, see Firefox/Shield/Heartbeat (MozillaWiki). The rating feature will establish a connection to Mozilla's servers at startup, which you can turn off like this:
Firefox will make use of the OpenH264 codec provided by Cisco in order to support the H.264 video codec in WebRTC, a technology allowing for peer-to-peer video communication on the web. For more information about this, see the OpenH264 Now in Firefox blog post.
The OpenH264 codec is not distributed with Firefox but gets downloaded at the first start of Firefox. In case you want to prohibit that, you will have to preconfigure the browser and set the media.gmp-gmpopenh264.enabled preference to false.
DRM contentTo disable this feature, see Watch DRM content on Firefox.
WebRTCWebRTC (Web Real-Time Communication) is a technology which provides direct browser-to-browser communication (audio, video, filesharing). As it is drafted and implemented at the moment, WebRTC can lead to your local IP address being exposed to websites even when you are behind a VPN or a NAT router – in the WebRTC API this data would be used to set up a peer-to-peer connection between two local clients.
For different methods and granular controls on how to mitigate this issue, see Media/WebRTC/Privacy Media/WebRTC/Privacy Media/WebRTC/Privacy Mozilla Wiki page.
Network DetectionFirefox's captive portal feature tests whether your network connection requires logging in, for example, on a public Wi-Fi hotspot, by regularly connecting to https://detectportal.firefox.com/success.txt. Firefox will also make connections to this URL to check if your current network supports IPv6.
To disable this feature:
If your computer is infected with a virus, trojan, spyware or other malicious software, then Firefox's Internet connection may be being piggybacked in order for the malware to communicate with its author or to deliver advertisements, etc. If you suspect this is the case, consider seeking advice from a forum specializing in malware removal. For more information, see Troubleshoot Firefox issues caused by malware.
Loopback connectionNote: This does not apply to Linux systems.
A loopback connection (to IP address 127.0.0.1) can be made by Firefox on non-Unix machines. In this case the browser is communicating with itself as expected, and it is not recommended that this communication be blocked. See bug 100154 for more information.
Based on information from Connections established on startup - Firefox (mozillaZine KB)
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