I guess one method to answer your direct question is Have a screen full of about:blanks followed by your three home pages. so that they are not visible and do not load. It seems a bit of an edge case though apparently wanting to set homepages, but not then wanting them to load. Most people may probably just use those as bookmarked pages and open them as and if required.

You appear to suggest you have three home pages set

• Set the homepage to about:blank , and to start from a homepage.
  Startup, home page, tabs, and download settings

Before you close down Firefox.

1. Close any tabs that are already bookmarked, and where you do not wish to modify that bookmark.
2. Right click any other remaining tab and use the option to bookmark all tabs.
3. Close down Firefox using the menu.
   Use Menu button{three bar icon) -> Shutdown Icon
4. When Firefox reopens it will be a blank tab.
5. Other tabs may be loaded and opened as required, either single bookmark at a time or or as a multiple tabs from a bookmarks folder.
   • Or alternatively opened from the History options. (In which case bookmarking is not essential).

• If you are attempting to improve loading time and bandwidth use; do not clear, or use settings that clear, your cache.
  Note How to clear the Firefox cache & Private Browsing - Use Firefox without saving history Tab preferences and settings

Also note by default Firefox does not load tabs that are not visible. So if you have more than say 12 tabs open but only 12 visible only those twelve visible tabs get loaded on startup.

By the way you may already have noticed but

• Startup, home page, tabs, and download settings

  Don't load tabs until selected: Firefox will only load the active tab when it starts or restores your previous session. This can make startup much faster if you are restoring many tabs. The other open tabs will be loaded as you click on them.

Flips the pref

browser.sessionstore.restore_on_demand

So you may be interested in restore_* prefs

As for the sessionrestore data that is a lot more complicated but see this discussion and post

• disable session restore
  • /questions/1068356#answer-746048

Note there are changes afoot with respect to per tab processes. A project known as Electrolysis or e10s that are working through to the Firefox Release

• See also /questions/1068635#answer-747642

I'm going to mark this as solved to close it but really I guess I've determined it's unsolvable. The answer to "How do I stop homepage tabs from loading in the background" is really "why would you want to do that?"

Mainly I want to do it because I use extra homepages as "view soon" reminders. If I bookmark something it's likely to be forgotten and lost, whereas if I at least see the tab whenever I start firefox, I'll deal with it eventually. I'll have to modify this behaviour, though, I suppose.

browser.sessionstore* -

My understanding of these settings after reading other questions is that they won't affect homepage loading, just tabs that were open at last close and will be reopened on a new start, if you have firefox set to operate that way. (Which I don't - if I close a session with 9 tabs, they're gone, and the next start will just spawn my homepage tabs.)

john99, I do appreciate your time and assistance.

Are you only reopening pinned tabs?

Firefox will open one normal tab when started, but should select a pinned tab if you close Firefox with a pinned tab selected.

There are these three prefs that determine the startup behavior:

browser.sessionstore.restore_pinned_tabs_on_demand (pinned tabs)(false)
browser.sessionstore.restore_on_demand (default as set in Options -> Tabs)(true)
browser.sessionstore.restore_hidden_tabs (tabs in other tab groups)(false)

I can see the idea behind opening Firefox without previous tabs. We often see problems where users have dozens or even hundreds of session tabs open, and come to rely on them always being there.

Mainly I want to do it because I use extra homepages as "view soon" reminders. If I bookmark something it's likely to be forgotten and lost, whereas if I at least see the tab whenever

Consider tagging the three important bookmarks say with "aaa" That you will always find them when needed just type aaa or + aaa into the addressbar.

• Address bar autocomplete suggestions in Firefox#w_changing-results-on-the-fly
  • Bookmark Tags - Categorize bookmarks to make them easy to find
• Or if you consider using pinned tabs Pinned Tabs - keep favorite websites open and just a click away

This trivial matter was driving me mad. I seem to have solved it? Open the page that you wish to set as home and 'cut' the address from that page. Open options tab and begin in 'General'. Remove the address from the Homepage box then paste the one for your selected homepage. Ta Dah?