Advanced SystemCare is incorrectly labeling those as "plugins" (honestly, anything by iobit is probably a piece of software I would not use).

Those "plugins" are actually built-in features of Firefox. They aren't third-parties, and aren't spying on you nor are they slowing down Firefox. They are broken out as "plugins" so they can be updated and developed independently

Hi denniswurban, check out the Troubleshooting Information page. You can open that using either:

• "3-bar" menu button > "?" Help > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter/Return

There are two relevant tables on this page:

(1) Firefox Features

These are extensions designated as system add-ons to add features to Firefox. Mine lists five extensions (I have bolded the ones I consider important to keep enabled):

• Firefox Monitor -- can report to you security breaches known to the Firefox Monitor service. The preference to disable this feature is extensions.fxmonitor.enabled (set to false in about:config).

• Firefox Screenshots -- to use the screenshot tool, click the Page Actions menu (•••) in the address bar. The preference to disable this feature is extensions.screenshots.disabled (set to true).

• Form Autofill -- for U.S. and possibly some other locales, stores and fills addresses on websites. To disable this feature, see: Automatically fill in your address on web forms.

• Web Compat -- this is a tool Mozilla uses to distribute site-specific patches that don't justify updating Firefox.

• WebCompat Reporter -- enables easy reporting of web compatibility problems so Mozilla can look at why a page renders poorly in Firefox. Mine is disabled (in about:config, extensions.webcompat-reporter.enabled is false by default).

(2) Extensions

This list mixes search engine plugins (previously packaged as .xml OpenSearch files, now packaged as .xpi extension files) with extensions you installed. Hopefully this will be sorted into different categories in the future.

The built-in search engine plugins in your list depend on your region/locale, but generally speaking, their ID should end with @search.mozilla.org. If you want to prevent Firefox from loading one or more of these, you can use a Policy file. Check my reply in this thread: when I open firefox, iobit uninstaller shows extra plug-ins.

1. Why are the vast majority hidden in Firefox Tools>Add-ons?

Features are managed through preferences, not through the Add-ons page.

Search engine plugins are managed through the Search panel of the Options/Preferences page.

2. What do these unwanted, secret add-ons do (here are a few: ebay (1.0), Amazon (1.1), Twitter (1.0), Bing (1.0), Wikipedia (1.0), Duckduckgo (1.0), Google search (1.0), etc)?

Those are search engine plugins. The packaging changed from OpenSearch XML files to extension XPI files.

3. Do they/can they spy on me? (some probably do, as some are listed as ‘reporters’ (e.g., Firefox monitor (3.0), Web Compat (5.0.2), WebCombat Reporter (1.1.0), etc)

No.

4. Do I have a choice?

These are parts of Firefox, you can disable nearly all of them.

5. How much do they slow down Firefox?

No idea, but nearly all of them do nothing until you activate them by clicking a button or performing a search.

6. Why do they return after I delete them using 3rd party software?

Because IObit software doesn't do what it says it does??

7. Why doesn’t Firefox allow me to delete them within Firefox?

Built-in items cannot be deleted, just disabled.

Thank you jscher2000,you answered all the questions I asked. It took me a while to digest your nice response. It leaves just one question I did not ask previously, I am wondering why some popular websites (ebay, Amazon, Wikipedia, etc) need special code (XPI files), whereas most websites do not and work fine with the basic Firefox (no dedicated XPI)?

denniswurban said

... I am wondering why some popular websites (ebay, Amazon, Wikipedia, etc) need special code (XPI files), whereas most websites do not and work fine with the basic Firefox (no dedicated XPI)?

Those aren't "websites" XPI's - those are the default Search engines that come with Firefox! And they vary by by the localization version the user installs.

Tyler calls them "built-in features of Firefox", but since they are packaged in an XPI file format I would call them "extensions / addons" that are provided by Mozilla whether you want them or not. As they are categorized in about:support. And the ID tells you what they are with @search.mozilla.org .

That is a fairly new manner of handing the "provided" Search engines, in the not so distant past they were hidden from the user in the omni.ja Firefox program files folderset where they would get installed (replaced) anew with every Firefox program update. I'm not sure when that change occurred, but it seems to me to have happened in Firefox 65, 66, or 67.

IMO, nothing nefarious, just a different way of handling Search Engines within Firefox and by Mozilla with the various download & updates servers that Mozilla employs.

The Web Compat extension adds support for the about:compat page that shows a list of websites that require a user agent override in order to work properly (i.e they do user agent sniffing in a way that breaks their website in Firefox).

• https://wiki.mozilla.org/Compatibility/Go_Faster_Addon/Override_Policies_and_Workflows

See also: https://bugzilla.mozilla.org/buglist.cgi?product=Web%20Compatibility&component=Interventions

Firefox comes with a large amount of builtin search engine to be able to support a lot of locales each with their own search engines.

• resource://search-extensions/
• resource://search-extensions/list.json

Previous Firefox versions (67 and older):

• resource://search-plugins/
• resource://search-plugins/list.json