There's no undo. It's probably not worth trying to restore a backup copy of the cookies.sqlite file unless you had some irreplaceable cookies. By that I mean, for example, a cookie that got you into a site where now you can't remember your account information.

It is worth it. I have a recent backup. What about the other two files: cookies.sqlite-shm cookies.sqlite-wal

Those are temp files used by the SQLite database engine. When Firefox shuts down, it reconciles and removes the temp files. Which I guess is to say, it's safest to remove the current temp files when doing the swap if Firefox doesn't. Do you need the old ones? I have no idea how to determine that.

well, I did it yesterday. I'll see if things seem to go back to normal.

Not quite back to normal. For instance, I have remained "signed in" to Yahoo Groups for many years. Now I'm not. But on my old computer, I am still signed in.

Also, it occurs to me that the cookie file must not be a unique Firefox file, because other browsers make use of it -- right?

Does the operating system (El Capitan on new computer, OSX 10.6.8 on old) have any cookie tracking function?

Hmm... I'm looking at my Yahoo Account Info on the old computer, and it shows a "verified" email address.

But when I type that into the new computer trying to sign in, it says "Sorry, we don't recognize this email."

WTF?

VerizonSucks said

Also, it occurs to me that the cookie file must not be a unique Firefox file, because other browsers make use of it -- right?

cookies.sqlite is unique to Firefox. I don't think any other non-Gecko browsers use Sqlite database files. But if that old computer is running the same version of Firefox (or close to the same) you could copy the cookies.sqlite file over to the new computer. Should be "interchangeable" from one Firefox installation or Profile to another.

VerizonSucks said

But when I type that into the new computer trying to sign in, it says "Sorry, we don't recognize this email."

Where are you entering it? Is this for a Firefox account login?

I'm trying to login to Yahoo Groups. So whatever key it was looking at has been lost, so must have been in the cookies file OR those two sqlite files which I trashed since we thought they were temp files.

So I guess I'll copy all 3 over from the old computer and see what happens.

Doesn't work. So is Yahoo detecting something about my "device" or some identifiying quality of this copy/version of Firefox?

whenever I startup Firefox on my old computer & open a Yahoo Groups page, I'm automagically signed in, and its been that way for many many years.

When you get the message "sorry we we don't recognize this email" can you tell what email address it is referring to?

Can you rule out a password manager as a potential complicating factor (either Firefox's built-in password manager or an add-on)?

Yahoo Sign In wants an email, not a password.

Its not stored in Prefs/ Security/ Saved Logins.

I don't have any security/password addons, just ad & tracking blockers

And it was working until I trashed all my cookies.

When you delete cookies from the menu, does it delete all 3 of those files???

Oh crap. That email is recent, created as a target to forward emails from Yahoo Mail. So it has nothing to do with my signing in.

I created a Yahoo username... more than a decade ago? I know my user name, but the sign in process is not asking for that.

In the RECENT past, I've sometimes had to input my Yahoo User Name. But now they want an email... maybe I can dredge it up from archives, if they sent a Welcome Message by email...

But the point is, what has been lost or changed that stops me from being automagically signed in, but only on THIS computer and not the OLD computer?

OK, I'm in. I had to enter a USER name even though it was asking for an EMAIL.

But I still don't know why it stopped automagically signing me in.

The sign in box does have a different appearance from what I remember.