https://www.macbookproslow.com/how-to-speed-up-slow-firefox/ this

https://www.macbookproslow.com/how-to-speed-up-slow-firefox/ this

Thanks for your help, but I have tried all those suggestions before, and they simply don't help. My problem only happens after waking my Mac from sleep - otherwise Firefox works as it should. Has anyone had this specific issue?

Step 1: If Firefox becomes totally unresponsive, force quit. If it turns out that the Mac machine is frozen, you’ll probably have to do a hard reboot by pressing the power button – holding it for three seconds, then press it again to restart your Mac.

Step 2: Open Firefox browser and check the version.

Click the Firefox icon on top left corner, you’ll see “About Firefox”. Click on it and a window will pop up showing you the current version you are using. If it’s not up to date, update it right away

Step 3: Lighten your browser.

You can do so by:

   Clearing browsing history (Firefox Menu > History > Clean recent history)
   Removing useless extensions (Firefox Menu > Preferences > Extensions & Themes > Extensions)
   Disabling unnecessary plugins (Firefox Menu > Preferences > Extensions & Themes > Plugins)

Step 4: Clean your Mac hard drive.

You can do this manually, or save time by using a dedicated cleaning app like CleanMyMac X. It will help tune up your overall Mac performance, as well as making Firefox run more smoothly.

Step 5: Better web browsing habits.

Always try to open only one window, and close tabs/pages you don’t need to read, especially when you finish reading content in big magazine sites like Forbes, Huffington Post, MacWorld, etc. which I view as heavy sites because they usually load tons of video ads automatically.

Avoid multitasking at all cost. When you are using Firefox, close as many other apps as possible to squeeze more system resources (CPU, RAM) for Firefox.

Step 6: Switch to an alternative web browser.

Sometimes Firefox just doesn’t work well with certain versions of macOS, for example the previous El Capitan. Many Mac users have observed the performance issue. See more from this thread: Firefox not happy with El Capitan (Apple Discussions)

If Firefox is still running slow or freezing randomly, use an alternative like Google Chrome or Apple Safari though they sometimes act up too.

Anyway, we hope these steps have helped you speed up Firefox a little bit. If you have any further questions, let us know by leaving a comment below.

Thanks for the suggestions, but they are the same ones as in the previous message, and they don't address my specific problem.

I have tried all of those things before, and also tried the Firefox Refresh feature, but the problem persists.

Has anyone found a solution that is known to work for my specific issue?

I thought I had finally identified the cause. I decided to have a closer look at all my F/F settings.

When I checked Preferences / General / Network Settings, I found "Configure Proxy Access to the Internet" was set to "Use system proxy settings". My Internet Service Provider recommends "No proxy", so that is what I changed it to.

Initially I did not have any further trouble, but the same problem has just happened again.

Still looking for a solution.....