A few years back, Google announced that it would be adding "tab discarding" to Chrome, emulating (on a basic level) the memory-releasing functionality of extensions like The Great Suspender. Although the feature was implemented a while ago, not much fanfare was made about it. If you're curious, it's easy enough to get a behind-the-scenes look.
First of all, make sure tab discarding is enabled via the internal
chrome://flags page. Just look for the setting visible in the image above. Note you'll need to restart the browser for it to start working.
Then, you can hit up another internal page by typing the following into the address bar:
chrome://discards. This will show you a rudimentary list ordering open pages "from most interesting to least interesting".
Pages deemed "least interesting" will be discarded by the browser if the system runs out of physical memory. Not an easy thing to achieve usually, but it's nice to know Chrome won't explode if there's such an occurrence.
What does "discard" actually mean? All Chrome will do is unload the tab's resources, while leaving it "open". As soon as you refresh the tab, those resources will be loaded back in. The idea is that tabs you haven't looked at in a while will, in effect, be "discarded" until you need them again. Chrome just assumes that, because it's been hours (or even days) since you viewed the tab, it's unlikely you need it ready to go.
For more information about how it works, there's a great Chrome developer post by Addy Osmani with extensive details.
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