Alt+F,K 

Menu {#bar icon) -> Tools 

Possible values and their effects
0  Check for a new version of a page once per session (a session starts when the first application window opens and ends when the last application window closes).
1 Check for a new version every time a page is loaded.
2 Never check for a new version - always load the page from cache.
3 Check for a new version  
when the page is out of date. (Default) 

Hi orschiro, I am not sure there is a method to do that as you would like, just with bookmarks, although Firefox may already be doing something similar. '''Firefox has a mode for working offline.''' This is a throwback to the days of when many people did work offline because the internet was slow and expensive. Use keyboard shortcut Alt+F,K That opens the menus toolbar then the File Menu and selects & toggles working offline. The option is I think also available from Menu {#bar icon) -> Tools (I am in Windows at present, Linux uses some different menu names and options to Windows) Note that by default Firefox will use cached pages and parts of pages when available, and should only renew them when it thinks they are outdated. (I think by default pinned tabs initially reload from cache). It is possible to alter the caching behaviour I am not sure you will need to but see * http://kb.mozillazine.org/About:config * http://kb.mozillazine.org/Browser.cache.check_doc_frequency Possible values and their effects 0 Check for a new version of a page once per session (a session starts when the first application window opens and ends when the last application window closes). 1 Check for a new version every time a page is loaded. 2 Never check for a new version - always load the page from cache. '''3 Check for a new version <br/>when the page is out of date. (Default)''' Also note that by default Firefox loads only visible open existing tabs, those in the background are not loaded until they are needed. If you are loading a large number of bookmarks you may consider toggling Firefox offline until all the tabs are created, then toggling it back online. You can check what Firefox does on individual tabs with the '''network tool'''. * https://developer.mozilla.org/docs/Tools/Network_Monitor ** '''cache comparison''' [https://developer.mozilla.org/docs/Tools/Network_Monitor#Performance_analysis] I have just opened up a current Release of Firefox. The performance tool on the Network console is present in Fx48 and displays a pie chart comparison of the cached content used normally or compared with a reload overriding the use of cache. You will probably find that of interest. <img src="https://mdn.mozillademos.org/files/12864/nm-performance.png" width=400>