Session restore inevitably makes connections when reloading -- at least one tab per window. I can't think of a way to defeat that, other than perhaps finding a way to start Firefox in offline mode. If you set offline mode when ending you session, does it stick when you restart Firefox?

File menu (or Alt+f) > Work Offline

Hi, thanks for a quick reply. Yes FF loads at least one tab, though I could opt out when I'm on "about:newtab", hence there shouldn't be even one IP address to connect to but zero, further on I have set FF to "browser.newtabpage.enabled;false". However, for the moment I have some 100 tabs or so, but even if I restart and land again on "about:newtab" where I opted out from last time, in my firewall one can see FF still connects to several tens of IP addresses.

I tried to set FF as Off-line before closing FF, but when restarting it's back on On-line mode, eg. Off-line check mark is gone. I am not sure what am I really missing here.

Just adding a quick note, this post is now written via a clean installation of FF 19.0.2 with "prefs.js" and "sessionstore.js" (which has a lot of "open tabs") copied from the FF 13.0.1, the problem is still there, FF connects to a bunch of IP addresses at start-up. edit: I just tried also restart with only "sessionstore.js" but with the same behavior.

According to this older thread, in order to force offline mode, you need to start up using Firefox's profile manager: How do I set the FF browser default to offline mode? ***I WANT IT OFFLINE***. Not sure whether that has changed since last August.

Ok, I should be honest I have been using the portableapps dot com version of FF 13 and 19, I tried the following on the FF 19: "C:\FirefoxPortable\FirefoxPortable.exe" -p "C:\FirefoxPortable\App\Firefox" -p but in both cases I were not able to start the Profile Manager, the second line wouldn't even start FF, in the first case FF started without opening the tabs but one tab, the FF start-search-page from where one could restore the previous session, the connections to the many IP addresses didn't occur until I hit the restore previous session. I thought for a while it wouldn't depend on whether one uses the portable version or not as I noticed another post with an apparently very similar case, link: http://support.mozilla.org/en-US/questions/930187

Try Portable Apps support.
http://portableapps.com/forums/support/firefox_portable

Ok, I have now installed an original version of Firefox 13.0.1, set it up with a basic set of few add-ons for safe browsing being as follow:

• NoScript
• RequestPolicy
• BetterPrivacy
• HTTPS Everywhere

In all cases described below, I browsed to a few pages, afterwards I go to an empty page/tab (about:newtab) before I close the browser, and is set to: "browser.newtabpage.enabled;false" in the hope also a newtab should be empty.

I also followed the instructions under the following link: https://support.mozilla.org/en-US/kb/how-stop-firefox-automatically-making-connections

• further on I have disabled a few other things under about:config to stop this "leak", such as webGL, telemetry, rename all google links, etc.

1st test

• I did restart in Off-line mode as described under the link given by jscher2000, when restarting the firewall shows no sign of connection to the internet, not even when I toggle from off-line to on-line.

2nd test

• with all add-ons enabled, I got the following result, see below for the list of IP numbers/info:
• 212.121.101.7 Server Location: Netherlands ISP: Routit BV
• 173.194.32.0 Server Location: Mountain View, CA in United States ISP: Google
• 173.194.32.4 Server Location: Mountain View, CA in United States ISP: Google
• 95.100.4.61 Server Location: Europe ISP: Akamai International B.V.
• 192.150.19.49 Server Location: San Jose, CA in United States ISP: Adobe Systems
• 78.129.207.59 Server Location: United Kingdom ISP: Iomart Hosting Limited
• 69.50.232.54 Server Location: San Jose, CA in United States ISP: Silicon Valley Web Hosting
• 82.103.140.42 Server Location: Denmark ISP: EasySpeedy ApS

3rd test

• I disabled all add-ons and closed browser, and started again, same result as in 2nd test, except that 212.121.101.7 was replaced by
• 37.0.87.7 Server Location: Netherlands ISP: Routit BV .

As this behavior has apparently nothing to do whether it's portable or non-portable version of Firefox, one can assume it has always been like this as at least between all versions from 13.0.1 to 19.0.2, as the portable version 19.0.2 behaves the same way. Let us not forget another user have experienced apparently the same issue under the following link: http://support.mozilla.org/en-US/questions/930187 Any more ideas how the browser user can take control over this behavior, or any suggestions what could be wrong?

You can set the new tab to blank, or more specifically, you can set the preference browser.newtab.url to about:blank to display the classic blank page. (Customize your Firefox New Tab page)

I don't know what those connections are. I took a different tack and watched Firefox load just my home page using the Fiddler2 debugging proxy. This lets me see the host names, which are more illuminating for me than the IP addresses. However, if the connection are made on ports other than 80 and 443, Fiddler might ignore them, I'm not sure.

I have now taken some time to check further how FF behaves on another machine which is very clean and it's the same thing using FF 15.0.1, also, I took the time and installed fiddler on my main machine and got it running

• (in FF case Fiddler is enabled through FF menu: Tools > Monitor with Fiddler > Force traffic to Fiddler, before Fiddler could sniff up anything).

The results are correlating with the tabs of previously opened web pages, the more tabs/visited URL's the more connections appears, I also noticed in Fiddler that many favicon.ico appears in the list, tried to disable favicon under about:config but no difference after restart. The connections I see in the FW is made on port 443 directly to FF, other connections on port 80 goes through the antivirus program, no other ports, and I tried the about:blank, but no difference. This leak doesn't look good, but I am going to check machines on a totally different location than my own.

It's confusing that you are testing 3 different versions of Firefox, but I think the behavior is fairly consistent: if you restore your previous session, and you are not offline, Firefox will start connecting to the pages in the restored tabs, not just the active tab, but other tabs as well.

Other than what you've set (switching browser.sessionstore.restore_on_demand from the default value of true to false, usually by using the checkbox in Options), I'm not aware of any setting that governs the non-active/background tabs during session restore. Further research is required...

Edit: sorry, part of that is backwards. It should say:

Other than what you've set (browser.sessionstore.restore_on_demand set to the default value of true, usually by using the "Don't load tabs until selected" checkbox in Options), I'm not aware of any setting that governs the non-active/background tabs during session restore. Further research is required...