Unfortunately, pinned tabs are stored in the same session history files as other open windows and tabs, and if you set Firefox to clear browsing history when it closes, then it will erase the session history files.

Some possible workarounds (these open normal tabs, not pinned tabs):

(1) Add all your pinned tabs to your home page(s) list: How to set the home page

But if you tend to open a lot of windows, this is not an attractive option because each window will have all those custom home pages, too.

(2) Bookmark the pages for your pinned tabs in one folder, then use the folder's "Open All Bookmarks" option to re-open all of those pages

Otherwise, maybe there is an add-on that could help? https://addons.mozilla.org/firefox/

Mozilla recently started up a new "Ideas" site at https://connect.mozilla.org/. I think if you have time, it would be a good idea to post there to get into the current feedback stream. (Use the "Ideas" section.)

That's disappointing. Thanks for your reply.

Maybe:

• https://addons.mozilla.org/firefox/addon/startupapps/

Thanks. It's close but the tabs the add-on opens at launch aren't proper 'Pinned Tabs' insofar as they occupy a full tab-width in the horizontal tab bar, rather than the condensed, icon-only width of a Pinned Tab.

Thanks. It's close but the tabs the add-on opens at launch aren't proper 'Pinned Tabs' insofar as they occupy a full tab-width in the horizontal tab bar, rather than the condensed, icon-only width of a Pinned Tab.

That's strange, when I test two URLs in a separate profile set to automatic private browsing ("Never Remember History") I get pinned tabs. I wonder why yours aren't pinned?