What tips ? This shows only this question so have no idea of what you tried.

please : go to the Firefox 3 Bar Menu --> Options --> Privacy & Security panel and under Permissions check (put a tick in the box) the setting to Prevent Accessibility Services from accessing your browser.

Monitor in Task Manager. Should stay below 2 gigs. If excessive then do below and monitor and change if need to...Test and go up again , go back down, it will eventually get a zone you and it can live with.

Go to the 3 Bar Menu then Options --> General --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 1 = No Multiprocessor = slow again. Try 2 Restart Firefox after making these changes please.

Please uninstall Flash 24.0 r0 as 100's of security issues. Flash Player Version: 28.0.0.126 Current Version https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, . . . .) Note: Other software is offered in the download. <Windows Only>

Please let us know if this solved your issue or if need further assistance.

thanks for your answer. I just referred to the tips contained in help section of firefox menu. I suppose you mean firefox 57.0.3 menu=>preferences=>privacy=>firefox data collection and use . Yes, all boxes allowing data collection were already ticked. Under "permissions there is only "prevent accessibility accessing your browser" and I obviously couldn't tick that box. Flash 24.0 couldn't be located in my ubuntu 16.04. I installed flash 28 instead. In the link to adobe there is no "firefox version", only ubuntu version or linux (deb, yum, tar). All other suggestions have been followed. Still too much CPU and 2.5 G of memory used. Thanks

Pkshadow said

What tips ? This shows only this question so have no idea of what you tried. please : go to the Firefox 3 Bar Menu --> Options --> Privacy & Security panel and under Permissions check (put a tick in the box) the setting to Prevent Accessibility Services from accessing your browser. Monitor in Task Manager. Should stay below 2 gigs. If excessive then do below and monitor and change if need to...Test and go up again , go back down, it will eventually get a zone you and it can live with. Go to the 3 Bar Menu then Options --> General --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 1 = No Multiprocessor = slow again. Try 2 Restart Firefox after making these changes please. Please uninstall Flash 24.0 r0 as 100's of security issues. Flash Player Version: 28.0.0.126 Current Version https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, . . . .) Note: Other software is offered in the download. <Windows Only> Please let us know if this solved your issue or if need further assistance.

"prevent accessibility accessing your browser" and I obviously couldn't tick that box.