Hello collaco,

Would you check your home page setting please :

Preferences => General => under Startup : Homepage and new windows

How to set the home page

Some extensions open a page when they are updated, so if an extension update regularly then you may see their page more often. You can check the extension's settings to see whether you can suppress these pages.

Thank you McCoy you're really fast (the first!) but -

unfortunately we've already tried everything that is mentioned or explained on the first 10 google search page results in particular - • adjusting the home page prefs • adjusting about:config prefs in older versions of FF before v66.0.3 (back to 2003) • stack exchange results (We really believe in any stack...portal!) • waisting time with esoteric rituals and prays....

Install one of the mentioned add-ons and then explain how you! stop it opening a tab at the next FF startup (osx 10.13.6) in detail - references to other pages with experiences others made are not wanted. If you have no personal experience in that topic - please...don't.

And I nevertheless thank you!

You mention plugins like Adobe Reader and VLC that are no longer supported, so what Firefox version are you using?

• Help -> About Firefox

FF Quantum 64-bit 66.0.3 Add-ons: Adobe Acrobat 18.0.8 Open in VLC 0.1.0 AdBlock 3.27.0

Would you try this please :

Type in the address bar about:config and press Enter (promise to be careful, if asked)

Type in the search bar and look for the preference :

extensions.getAddons.cache.enabled

and set its value to false

Then close and restart Firefox.

If this doesn't make a difference, change the value back to 'true'.

After erasing FF, profile and all related stuff I've installed FF from the ground and now it works. Whatever caused that strange behaviour is history.

However thanks for the support!

Hi, This condition started after I properly ran routine diagnostics, Disk First Aid, CRON jobs, etc.

Mac System Sierra Firefox 68.0.1 (64-bit) Undesirable tabs that open upon FF startup are: - Ghostery Hub Home - Adobe Acrobat Externsion for Mozilla Firefox - Evernote Web Clipper Quick - Tampermonkey Firefox

Ghostery, Adobe, and Evernote web pages are to encourage the use of those extentions which I already use. The Tampermonkey web page is a requirement for end user licensing. None of these web pages provide a means to prevent their appearing upon FF startup.

Yes, I tried all fixes thus far in this message thread.

Totally erasing FF and starting over, building up everything like it was, will require an exhorbant about of time, and, sooner or later the problem will recur and require same time consuming re-building of FF. The ground up reinstall amounts to kicking the can down the road.

There are many web sites that provide solutions for Microsoft Windows users, but search engine searches for Mac solutions are nil, unless such a fix is well hidden.

There has got to be a better, more efficient, way of resolving this. The Windows community can do it, so surely the Mac community can.

Any enlightenment, will be most highly appreciated.

Thanks very much.

You can check for problems with the extensions registry files in the profile folder.

Try to to reset the extensions registry and rename extensions.json (extensionsOLD.json) and rename/remove previously used extensions files like extensions.ini and extensions.sqlite when present and rename/remove compatibility.ini in the Firefox profile folder with Firefox closed.

• https://support.mozilla.org/en-US/kb/Profiles

New files will be created when required.

See "Corrupt extension files":

• https://support.mozilla.org/en-US/kb/unable-install-add-ons-extensions-or-themes

You can check for possible updates in case of issues.

• click the cogwheel button (left of the Search bar) on the about:addons page to "Check for updates"

If this didn't help then delete add-ons.json and possibly prefs.js in case there is a problem with preferences.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Hi Cor-el, Thanks for your fast reply. Not solved yet.

I carefully tried each of the above steps. After the first 2 the unwanted web pages again appeared in subsequent tabs.

I deleted occurrences of extensions.ini and extensions.json. Extensions.sqlite wasn't present. I did an add-on check for updates and there were none.

Cleared history, restarted FF, unwanted web pages in tabs persisted.

I tried various things in the settings, and finally ran out of things to try.

I took a look at what some Windows users do, to remedy this, and was unable to find any of their fixes that I could apply here.

Again, thank you for replying, especially on a weekend.

Hi Cor-el

Problem solved - UNKNOWN what solved it.

As stated above, I tried your suggestions, and restarted FF when I was supposed to, and unwanted tabs with web pages persisted.

Later I shut down the Mac, did other things, came back later booted up. Launched Firefox only my home tab appeared as it is supposed to.

I have no idea what fixed the problem.

If I may speculate, cold-rebooting the Mac, after applying one or more of your excellent suggestions, worked.

Please ask Firefox developers to determine, specifically, what fixes the [extra tabs with unwanted web pages] problem.

Many thanks!!!