browser.tabs.onActivated.addListener(async tabChange => { const activeTabs = await browser.tabs.query({ active: true }); const currentWindow = await browser.tabs.query({ currentWindow: true, active: true, }); if ( activeTabs.length === 1 && activeTabs[0].id == tabChange.tabId && currentWindow.length === 1 && currentWindow[0].id === tabChange.tabId ) { browser.tabs.remove(tabChange.tabId); } });