Empty Cache Button {web link} Cache clearing made easy. One click.

Type about:preferences#privacy<enter> in the address bar. The button next to History, select Use Custom Settings.

At the bottom of the page, turn on Clear History When Firefox Closes. At the far right, press the Settings button. Turn on Cache and Form And Search History.

when I open a page with a lot of large images, Firefox obtains a lot of memory and doesn't release it after heavy tab is closed.

Can you post a link?

Garbage collection and cycle collection on about:memory page don't help.

What about 'Minimize memory usage'?

Also see https://support.mozilla.org/kb/firefox-uses-too-much-memory-ram

Can you post a link?

joyreactor.cc :)) It's a russian entertainment site like yours reddit or 9gag. Problem appears on other sites too, but other sites usually don't have a lot of large pictures, so that serious performance issues appear after a long time.

What about 'Minimize memory usage'?

nope :((

One more notice: the problem doesn't appear on my desktop with Windows 10 installed, only on the laptop with Windows 7. Desktop has firefox version ESR 45.6.0 installed, laptop has the latest 50.1.0. Will try install esr on laptop.