Chosen solution Some Firefox 74 users are having problems with websites that require certain types of local storage such as Gmail and Twitter. The sites won't load in regular windows, but will load in private windows because private windows use memory-based storage and don't need to access the disk-based storage files used in regular windows. These users also have failures on the second through fourth tests on this page: https://firefox-storage-test.glitch.me/ If that matches the problem you're having: Past advice related to that diagnostic result was as follows: (1) Next Gen Storage Setting This setting is normally false (off) but in case it somehow got turned on, see the steps in the following article: Some pages or page elements fail to load after updating to Firefox 70. If that doesn't fix it (after a restart, perhaps): (2) Flush Data for Problem Site(s) If you tell Firefox to remove all data for a site, that should include removing its storage folder, as well as its cookies, history, and customized permissions. If you don't want to remove all data, you might be able to fix it temporarily by just removing the "cookies and site data". Here are how to access these options: (A) Cookies and Site Data Open the Options/Preferences page using either: 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, scroll down to the Cookies and Site Data section Click the Manage Data... button to open the "Manage Cookies and Site Data" dialog. In the dialog's search box, type goog to filter the list. Select the domain(s) relevant to Gmail and click the Remove Selected button. Then click the Save Changes button at the lower right. Any difference when you try the site again? (B) Forget About This Site Open the Library window using Show all History (Ctrl+Shift+h) In the small search box at upper right, enter enough to uniquely identify the site, such as mail.goo -- we want to avoid accidental misclicks with this feature Right-click a matching history entry and choose Forget About This Site Because Firefox modifies a number of files, this may take some time to run. Any difference? If that doesn't fix the problem site(s): (3) Have Firefox Generate New Storage Folders This will cause loss of some data saved locally by websites and add-ons. Open your current Firefox settings (AKA Firefox profile) folder using either "3-bar" menu button > "?" Help > Troubleshooting Information (menu bar) Help > Troubleshooting Information type or paste about:support in the address bar and press Enter In the first table on the page, on the Profile Folder row, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows/File Explorer. Leaving that window open, switch back to Firefox and Exit, either: "3-bar" menu button > Exit (menu bar) File > Exit Pause briefly while Firefox finishes its cleanup, then right-click the storage folder and Rename to something like storageOLD -- the purpose of renaming instead of deleting is the possibility of reinstating the old folder or mining it for essential data.