Tab Cap от Jon Breen

Tab Cap keeps a small set of tabs in memory and unloads the rest. Unloaded tabs stay in the strip with their title and favicon. Coming back reloads the page, so forms, scroll position, and in-page state are gone unless the site saved them.

In memory is the limit — 1, 5, or whatever you set on the toolbar button. The oldest tabs unload first. The badge is 2/5: two ordinary tabs in memory, limit five.

Always load this tab (popup, tab context menu, or Ctrl+Shift+K) keeps that tab warm. Always-loaded tabs do not count toward the limit. Pin mail, mark a draft, and still run a cap of 1 on everything else.

Unloading on the same popup turns the whole thing off. Right-click the Tab Cap button for the same switch.

Firefox-pinned tabs and tabs playing sound are treated as always-loaded by default (optional, under More options). Firefox will also refuse to unload a page that would show a leave-this-site prompt.

Tab Cap does not collect or send browsing data.