How can I use Firefox locally, preventing it from going online at all?
For my own reasons, I want to use Firefox to view files that are local to my machine (file:///<filepath>) without connecting to the internet; but "Work Offline" seems to allow connections to go through.
I have searched for solutions on the web, but they either discuss blocking only certain resources or certain websites. That's not what I want; I want Firefox to stay completely offline when I'm working with my files.
Is there a way to do that?
Press Alt or F10 to bring up the toolbar. Menu > File > OffLine
No, that doesn't work. Even though the "Work Offline" option is checked (as it is right now as I send this response), Firefox still opens pages from the internet, e.g. this Mozilla Support page. I don't understand just what the "Work Offline" option does, but it certainly doesn't block Firefox from using an existing internet connection; perhaps it's intended to allow one to access local resources when there is no internet connection, but not to prevent access when there is one?
That is strange. Open your Firewall. Find the Firefox entry and block it. Not remove, block.
There are no rules in my iptables that mention Firefox.
That's right, even that page opens while "Work Offline" is checked.
Are you sure that the page isn't loaded from the cache?
Can you reload the page (Ctrl+R or Shift+Ctrl+R)?
Can you confirm that actually network traffic leaves the computer?
I verified that "Work Offline" is in fact checked before I performed these checks.
"Are you sure that the page isn't loaded from the cache?" Yes. I cleared the cache, but even with "Work Offline" checked, pages load from the network.
"Can you reload the page (Ctrl+R or Shift+Ctrl+R)?" Yes. and I can see messages at the bottom of the window about connecting, waiting, etc.
"Can you confirm that actually network traffic leaves the computer?" Yes; according to your network monitor, traffic is moving across my network interface.
Is your computer plugged into a phone line or are you using a modem/WiFi? You can unplug them for the same offline result until this issue is solved.
I am using an Ethernet connection to connect via router to my satellite transceiver. To dis/reconnect the cable I will have to continually crawl around behind/under various pieces of furniture; not at all convenient.
I get the impression that Work Offline is not intended to enforce offlineness as much as to allow web apps to work while the network is unavailable, the opposite of what I am trying to do?
OffLine means the browser should not connect to the outside world. I checked my Firefox (v54) and offline does work.
I also checked my v59.0.2 and offline works.
The attachment shows what I'm running. It definitely does Not prevent connections to the outside world. Is it possible that there's something in about:config that could be related to this?