You can check this urlbar pref on the about:config page.

• browser.urlbar.autoFill = true

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Thanks for that suggestion. The option is set to true. To make sure it was set, I toggled it to false and back to true. It still doesn't autocomplete the URL the way it used to.

(Windows 10, build 1909, BTW)

I had five extensions installed - I disabled them but it didn't fix the problem.

I uninstalled Firefox and reinstalled it, clean, same problem.

If you use Sync then best is to disconnect Sync temporarily during troubleshooting.

You can check for problems with the places.sqlite and favicons.sqlite files in the Firefox profile folder.

• use "Verify Integrity" button on the "Help -> Troubleshooting Information" (about:support) page

If errors are reported with "Verify Integrity", close and restart Firefox and retry.

If "Verify Integrity" cannot repair places.sqlite, rename/remove all places.sqlite and favicons.sqlite files in the Firefox profile folder. Firefox will rebuild places.sqlite and restore the bookmarks from a recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created

See also:

• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file
• https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional

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 Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

I tried the Verify, it said: > Task: checkIntegrity + The places.sqlite database is sane + The favicons.sqlite database is sane > Task: invalidateCaches + The caches have been invalidated > Task: checkCoherence + The database is coherent > Task: expire + Database cleaned up > Task: originFrecencyStats + Recalculated origin frecency stats > Task: vacuum + Initial database size is 5120KiB + The database has been vacuumed ...

That didn't fix it. I went to about:profiles to delete the two files you said, but it says "This is the profile in use and it cannot be deleted." Should I rename them? Close Firefox and delete the files?

Later: I created a new profile, same problem.

For what it's worth, I tried an experiment in a new profile that had never visited Amazon.

(1)

I submitted amazon.com in the address bar. Firefox redirected and loaded https://www.amazon.com/

I used a bookmark to go to to a different page. When I typed am in the URL bar, I did not get any autofill suggestion (a gave me a different site).

I used the drop-down to load https://www.amazon.com/

I used a bookmark to go to to a different page. Now when I typed a in the URL bar, I got https://www.amazon.com/ as the autofill suggestion.

(2)

In the Library window (Ctrl+Shift+h), I used "Forget About This Site" to erase Firefox's memory of Amazon.

I submitted a search for amazon and clicked the result link to https://www.amazon.com/

I used a bookmark to go to to a different page. When I typed am in the URL bar, I did not get any autofill suggestion (a gave me a different site).

I went back to the search results and repeated those steps. Still no suggestion.

I went back to Amazon and bookmarked it. I used an older bookmark to go to to a different page. Now when I typed a in the URL bar, I got https://www.amazon.com/ as the autofill suggestion.

I went to the Library (Ctrl+Shift+b) and deleted the Amazon bookmark.

Now when I typed am in the URL bar I got no suggestion.

(3)

In the Library window (Ctrl+Shift+h), I used "Forget About This Site" to erase Firefox's memory of Amazon.

I pasted the full URL https://www.amazon.com/ in the address bar and pressed Enter to load it.

I used a bookmark to go to to a different page. When I typed a in the URL bar, I got https://www.amazon.com/ as the autofill suggestion..

Conclusion

Firefox seems requires particular actions before it will suggest a site in the address bar such as

• Loading the final URL from history
• Bookmarking the page
• Typing the final URL in (or copy/pasting the final address to) the URL bar and submitting it there

Possibly other methods of accessing a site may trigger an autofill suggestion if repeated over time, but that is what I saw in this test.

It's possible this is different from older versions but since I disable this feature, I wouldn't know.

That seems to be a different behavior from before. Version 75 was released 11 days ago - I wonder if something got messed up.

Followup: my laptop running the same version and the same version of Windows does NOT have the problem.

I'm thinking I need to completely wipe Firefox and its files. When I was reinstalling, it said that it was keeping some files.

Later: I uninstalled Firefox (again), and deleted the folders the instructions said to delete, including one in %appdata%. I reinstalled it, and the problem still exists.

Well, now it started working again!