Hi lingo242, 2GB/hour seems like an excessive amount of space for just visiting websites. Can you tell what folders have grown, for example, Downloads, or various Mozilla folders?

Firefox uses two temporary folders you can flush with minimal consequences:

(1) Cache

As you browse, Firefox accumulates chunks of HTML, style sheets, scripts, and images to accelerate reloading of the page. To see the location of your cache folder, type or paste about:cache in the address bar and press Enter to load it. My disk cache currently uses about 646MB.

Since cached files are not essential -- Firefox can simply request them again on your next visit -- you can clear the cache any time you like. See: How to clear the Firefox cache. When doing that, be careful not to clear data you really do want to keep, such as browsing history. There's no "undo."

(2) Other Temp files

Firefox uses the Windows Temp folder (usually under your individual Windows user profile). Windows has built-in features to clear the Temp folder; they usually pop up when your disk space goes below 10%.

To manually open the Temp folder, type or paste

%TEMP%

in the Start menu search box and press Enter to load it.

Websites also can store data for offline access. To see what data sites have asked Firefox to store, try the dialog on the Options page:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the left column, click Privacy & Security.

On the right side, in the Cookies and Site Data section, click the "Manage Data" button. Here you can flush data for individual sites that you feel is no longer needed. (There is a "Save Changes" button at the lower right. If you can't see that button, use the "grippy" control at the lower right to expand the dialog.)

In addition to the above, Firefox stores thumbnail images, health report data, and numerous other bits and bobs. I don't know that these would use a noticeable amount of space, certainly not within an hour.

And of course add-ons can store a wide range of data, from snapshots of your sessions (so you can restore various sets of tabs later), to downloads (e.g., Mega),to who knows what.

As a test, you could browse for an hour in Firefox's Safe Mode. In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" Help button > Restart with Add-ons Disabled
• (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any difference in disk use?

I once had the same problem. Turned out to be malware.

Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.