You can also force the hibernation of a tab using the bookmarklet available here.

That bookmarklet can also be used to un-hibernate a tab if you don't have the userscript running.

I am not maintaining this script so frequently these days. Because I started to use some other approaches for auto-suspending tabs.

First:

• https://chrome.google.com/webstore/detail/the-great-suspender/klbibkeccnjlkjkiokjodocebajanakg?hl=en

• https://addons.mozilla.org/en-US/firefox/addon/auto-tab-discard/

Then:

• https://chrome.google.com/webstore/detail/tab-wrangler/egnjhciaieeiiohknchakcodbpgjnchh?hl=en

• https://addons.mozilla.org/en-US/firefox/addon/tabwrangler/

I also found less need on Firefox because reopening an old session only loads pages lazily.

By the way, for managing your tabs, you could try:

• https://chrome.google.com/webstore/detail/tab-manager-plus-for-chro/cnkdjjdmfiffagllbiiilooaoofcoeff?hl=en

• https://addons.mozilla.org/en-US/firefox/addon/tab-manager-plus-for-firefox/