Also, if you still have memory/performance problems, these two addons make a noticeable difference:
- LoadTabOnSelect: Load new tabs on selection. This addon will prevent new tabs from automatically loading, instead loading them on selection.
The intended usage of the addon is to facilitate power-users who open many tabs before viewing, but dislike auto-playing videos (and other annoyances).
https://addons.mozilla.org/en-US/firefox/addon/loadtabonsele...
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- Auto Tab Discard: Use native tab discard method to automatically reduce memory usage of inactive tabs. Auto Tab Discard a lightweight extension that uses the native method (tabs.discard) to unload or suspend browser tabs to significantly reduce the memory footprint of your browser when many tabs are opened.
https://addons.mozilla.org/en-US/firefox/addon/auto-tab-disc...
edit: typos