Firefox Slow to Startup, Using Large Amounts of RAM?

Part of my structure and workflow with browsers – Firefox in this case – and one of the innovations I use to structure my browser is Pinned Tabs. Depending on the browser – different machines have different contexts and so different sets of Pinned Tabs in their browsers – I could have between 6 and 12 tabs pinned in the tab bar.

It took quite a while for me to realize it, but slowly my browser startup and performance was becoming very poor. Especially for those occasional links clicked when Firefox is not already open. Today it occurred to me that I’m well aware that Normal Tabs load their content on-demand when first switched to, and not immediately on browser startup. But is this the same for Pinned Tabs?

A quick test showed that Pinned Tabs load all their content immediately when the browser is started. I had my most resource-heavy web apps in those pinned tabs (Webmail, Slack, Trello, Feedly, and more) and they were inflating the startup memory overhead of Firefox by hundreds of megabytes.

Fortunately, as with most things Firefox, in about:config it’s a quick change to browser.sessionstore.restore_pinned_tabs_on_demand to prevent those heavy pages from loading immediately on browser start and rather have them load more comfortably when I actually need them.

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