Memory Saver Hero by Chris

Memory Saver helps reduce Firefox’s memory usage by automatically unloading tabs you haven’t used recently. Sleeping tabs remain visible in your tab bar and reload normally when you return to them.
You remain in control of how and when tabs are unloaded.

Features:

• Automatically unload inactive tabs after a configurable amount of time.
• Choose how frequently Memory Saver checks for unused tabs.
• Keep a minimum number of tabs loaded in each window.
• Protect pinned tabs and tabs playing audio.
• Protect specific websites and domains from being unloaded.
• Manually unload eligible tabs across Firefox or only other tabs in the current window.
• View all currently sleeping tabs in one convenient list.
• Restore or close sleeping tabs directly from the popup.
• Optionally record local foreground active-tab time with configurable retention.
• Clear locally stored activity data at any time.
• No advertisements, tracking, analytics, or data transmission.
• No access to webpage contents.
• Open-source software.

Memory Saver uses Firefox’s native tab-discarding functionality. It does not close sleeping tabs or remove them from your session—it simply releases their loaded content until you need them again.

Optional activity history is disabled by default. If enabled, URLs, titles, timestamps, and foreground durations are stored only in your local Firefox profile and are never transmitted anywhere.