When a session is restored, tabs are reloaded when selected. IMHO, the user should have the option to have pages displayed as they were previously when the session was closed, using the cache.
I believe this was default behavior at some point in the past.
I find this auto reload annoying because most of the pages don't change. This auto reload leads to delays and requires to login again if the page is protected. The latter is now getting a serious problem for me as most of the pages I use are login protected.
Another example, is say when you have to work off-line (e.g. in a plane) and look at pages that are restored from a previous session.
This very issue was reported some time ago. The thread was closed, with no workable solution (the 'work off-line' option in the 'File' menu does not fix this issue): https://support.mozilla.org/en-US/questions/918496
Thanks for your help,
This is probably the "Don't load tabs until selected" feature, which helps speed up Firefox on restarts as it only loads the tab you are currently viewing, saving time on the startup. You can change this by going to Options, then Tabs, then uncheck "Don't load tabs until selected".
Set the Integer pref browser.sessionstore.max_resumed_crashes to 0 on the about:config page to get the about:sessionrestore page immediately with the first restart after a crash has occurred or the Task Manager was used to close Firefox.
That way you see if a sessions has crashed or otherwise didn't close properly and will allow you to deselect the tab(s) that you do not want to reopen, but will allow to reopen other tabs.
Thanks for your answers - but this is not helping.
The 'Don't load tabs until selected" is on, and doesn't help. I don't want the tabs to reload (from the internet) at all!. I would like them to be stored in the cache, and be displayed as they were previously.
I believe the sessionrestore page doesn't apply, because I would like all tabs to be opened as they were when the sessions ended (nothing crashed here).
Maybe I am not clear enough. The same issue appear after a resume from suspend/hibernate : when selected, tabs get reloaded from the internet (causing delays, re-logins), whereas I'd like them to be reloaded from the cache: i.e. simply displayed as they were before.
It's got something to do with the duration a page stays in the cache, or caching being overridden by the session manager. Could be also cache cleared on exit.
I think you misunderstood me, you want to turn the "Load tabs until selected" off, uncheck that box. Also, make sure that you have a large enough cache.
When "Don't load tabs until selected" is unchecked, it seems that all tabs are being downloaded when I restart FF. So that is not helping either.
I've increase the cache to : browser.cache.disk.capacity:1048576
and disabled checking for a new page version: browser.cache.check_doc_frequency:2
I have a total of about ~100 tabs opened in ~3 windows.
FF takes about 512Mb RAM
Strangely, the cache size is only 21Mb (tool > options > advanced > network)