Very slow facebook and instagram loading when using firefox on my Macbook Pro laptop.

If you restart into Troubleshoot Mode from the Help menu to eliminate any addon interference, is there any change? When you sign in to these services using a new Private Window does anything improve that way?

Normally this happens on Windows when using various antivirus or security solutions trying to decrypt the the secure connections, I don't expect you would run something like this on a Mac, but to make sure, if there's anything scanning for virus/phishing/malware or you use some endpoint security, could you disable anything that touches connections, as "https scanning" or "secure web" etc. — or perhaps any VPN you might use?

jbr, Thank you for your reply.

Restarting in Troubleshoot in Help didn't help.

Signing in using a new Private Window however did avoid the slow loading.

I do use VPN sometimes but am not using it when the slow loading is happening..

Does any of this help find the cause?

Okay so in Private Window you get a fresh session with them, so it clears their previous tracking, versioning experiments, anything they store with you etc. so it points mostly at stale site data.

Maybe you missed some of their extra domains when clearing the caches? Or maybe have allowed tracking exceptions for their site in normal mode that then help them save more crud? Dunno, I'd generally try:

1. Start with clearing Firefox cache (for every site and all duration, temporary files are safe to drop without any impact).
2. If it does not help, try clearing cookies and data for the website you experience troubles with (warning: you will be logged out on this website) — the article shows the method via toolbar shield's "Clear cookies and site data" for the location currently open, which might help track more partitions and preferences granted for the sites.