Resetting preferences (zoom, tabs, privacy, network, encryption, updates, where to save file downloads, etc.) is one of many procedures that can be helpful in troubleshooting Firefox problems. We'll explain two ways to do this.

• If changes to preference settings are not saved when you restart Firefox, see 如何修正偏好設定無法儲存.

Solution 1: Refresh Firefox

The refresh feature restores Firefox to its default state while saving your essential information. This solution will reset preferences but will also remove other customizations, including added extensions and themes. For more information, see 重設 Firefox - 輕鬆解決大部分的問題.

Solution 2: Delete Firefox preference files

1. • 點擊選單按鈕，點擊 說明並選擇更多疑難排解資訊。在 說明選單點選更多疑難排解資訊。疑難排解資訊將會開啟。
   • 在應用程式一般資訊段落下方，可找到設定檔資料夾設定檔目錄，點擊開啟資料夾在 Finder 顯示開啟目錄。將開啟包含您的設定檔目錄。將開啟您的設定檔資料夾。
   註： 若點擊開啟資料夾之後，Firefox 顯示錯誤，或如果您無法開啟或使用 Firefox，請依照下列文章的指示操作：在不開啟 Firefox 的情況下尋找設定檔。
2. 點擊 Firefox 選單，然後點擊結束。點擊畫面頂端的 Firefox 選單，然後選擇離開 Firefox。點擊 Firefox 選單，然後選擇離開。
3. Locate and delete the file prefs.js (or rename it, for example, to prefs.jsOLD, to keep the old file as a backup). If you find more than one, a prefs.js.moztmp file or a user.js file, delete (or rename) these as well.
4. You can close the profile folder and open Firefox now.