Have you tried installing Add-on Compatibility Reporter?

It will tell you which add-ons are incompatible with multi-process.

Alternatively, you could try to revert those two mentioned keys to their default values and see what happens.

I did install Add-on Compatability Reporter. It says all my add-ons are multiprocess compatible, except that disabled one that I mentioned before (Norton Security). The troubleshooter used to say that multiprocess was disabled by add-ons, but no longer. Now it says it's disabled by accessibility tools.

I'll try resetting the two options though. It contradicts other advice, but it's worth a try.

If it doesn't work, you can always restore them to their previous values.

I found something specific, anyway, here. Quotation: Keep in mind that disabling accessibility may break some integration, notably could affect touch screen interactions. Try going to about:config in the URL bar and setting accessibility.force_disabled to 1** - then restart Firefox and check about:support again".

Thanks for the pointer. Setting accessibility.force_disabled to 1 got me multiprocess enabled, which definitely does speed things up. The problem I have then is that printing doesn't work. Printing anything sometimes gives me a Print Error message and always the printer spits one one blank page. I tried many different things: disabling all extensions, safe mode, and creating a new profile with nothing much n it, None of it solved the problem. The only thing that does is getting multiprocess disabled. Any thoughts?

Did you try reinstalling the printer drivers?

Try to set security.sandbox.content.level on the about:config page to 1 or to 0 if 1 doesn't have effect.

See also:

• https://wiki.mozilla.org/Electrolysis/Accessibility

Thanks to both of you for the suggestions.

I set security.sandbox.content.level to 0 (it was already 1), but that made no difference.

I have quite a few printer drivers, some for hardware printers and some for software printers:

Hardware:

HP Officejet Pro 8600 (Network), the default printer Epson Stylus Photo 1400 Series; it was turned off and so did not appear in the printer list when I was testing Fax; part of Windows, for a fax modem, I think. I don't have a fax modem though. Fax - HP Officejet Pro 8600 (Network); this printer does have fax capability

Software:

HP ePrint + JetAdvantage (part of the HP printer software) Microsoft Print to PDF (part of Office 365) Microsoft XPS Document Writer (part of Office 365) PDF995 (a cheap package for printing to a PDF file that I've had for a long time) Quicken PDF Printer (part of Quicken 2017) Send to OneNote 2016 (part of Office 365)

So it's a fair amount of work to reinstall them all. Are there some that are more likely to be the problem? Perhaps the one that I am actually using when testing, HP Officejet Pro 8600 (Network), the default printer?

I tried reinstalling the driver for my default printer, the one I was using, but that didn't work.

I tried something else too. I created a new profile. It had two extensions loaded, both disabled: Norton Security Toolbar and RoboForm Password Manager. I don't know of a way to completely get rid of the Norton extension without completely uninstalling the product. For RoboForm, I turned off Firefox support in RoboForm Options and that completely got rid of the RoboForm extension. There were three plugins loaded: OpenH264 Video Codec, Shockwave Flash, and Widevine Content Decryption Module. I changed all of them from Always Activate to Never Activate. Then I restarted Firefox and tried to print. It still failed the same way: just printed one blank page. By the way, I am using the 64-bit version of Firefox. It spoiled me, the 32-bit version won't let me open all the windows I want any more.

Sorry, I realized I misspoke in the previous message. I actually did the test with the 32-bit version. I went back and did it again with the 64-bit version. Got the same result. I did forget to remove the RoboForm extension, though. It was disabled, however.

P.S. - Sorry about all the replies.

You can try to disable multi-process windows in Firefox by setting these prefs to false on the about:config page.

• browser.tabs.remote.autostart = false
• browser.tabs.remote.autostart.2 = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

• http://www.ghacks.net/2016/07/22/multi-process-firefox/

I don't want to disable multiprocess windows, I want to have them, but I want printing to work too. Anyway, I now know how to get multiprocess windows enabled and disabled at will. My current problem is that when multiprocess windows are enabled, Print doesn't work (it just prints a single blank page).