Windows 10 reached EOS (end of support) on October 14, 2025. If you are on Windows 10, see this article.

Avatar for Username

Mozilla サポートの検索

サポート詐欺に注意してください。 私たちはあなたに通話やショートメッセージの送信、個人情報の共有を求めることはありません。疑わしい行為を見つけたら「迷惑行為を報告」からご報告ください。

詳しく学ぶ

このスレッドはアーカイブに保管されました。 必要であれば新たに質問してください。

Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.

  • 2 件の返信
  • 192 人がこの問題に困っています
  • 270 回表示
  • 最後の返信者: mjbrm
  • アーカイブに保管済み

2medusa
2medusa

I attempt to open firefox and despite firefox NOT being open I get the following message "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system."

Once restarted it works fine but does re-occure

I attempt to open firefox and despite firefox NOT being open I get the following message "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system." Once restarted it works fine but does re-occure

すべての返信 (2)

teleguy
teleguy

Press CTRL+ALT+DEL, open the task manager and click on "Processes". If Firefox is still running you can close it from there. Not a complete fix but it spares you the reboot.

mjbrm
mjbrm
  • Moderator

Hi,

This is a currently reported bug and it's being worked on. Mozilla will release an update to 29 tomorrow to fix some of the most commonly reported issues in the forum. You can either wait for the update or you can try the workarounds.

One workaround is to set network.seer.enabled to false

  • Navigate to about:config in your Address Bar
  • Press the "I'll be careful, I promise!" button to proceed
  • search for network.seer.enabled
  • Set that to false by right clicking and selecting Toggle