How do you enable vertical tabs and the AI sidebar in Firefox?
Turn on the sidebar introduced in Firefox 136 to move your tabs to the left and dock the AI chatbot of your choice.
Short answer
Update Firefox to version 136 or later, then go to Settings > General > Browser Layout and tick "Show sidebar". Once the sidebar appears, open its customize section at the bottom and switch on "Vertical tabs" plus the AI chatbot you want to use.
What you need
Step by step
Update Firefox
Open the menu button at the top right and go to Help > About Firefox. The window downloads any available update on its own, then click "Restart to update". None of the sidebar features exist in versions older than 136.
Turn on the sidebar
From the menu, open Settings > General and find the Browser Layout section. Tick the "Show sidebar" box there. The bar shows up on the left edge of the window and gives you history, bookmarks and tabs in one place.
Switch on vertical tabs
Click the settings button at the bottom of the sidebar, open "Customize sidebar" and tick "Vertical tabs". Your tabs move from the top strip to the left column. Titles stay readable even when the window is narrow, which suits anyone juggling a lot of tabs.
Pick an AI chatbot
In the same customize panel, enable the AI chatbot option and choose from the list: Anthropic Claude, ChatGPT, Google Gemini, HuggingChat or Le Chat Mistral. You will be asked to sign in to that service. The bot then sits in the sidebar ready to summarise text or describe an image while you browse.
Connect tabs from other devices
Sign in with your Mozilla account and turn on sync, and the tabs open on your phone appear in the sidebar too. Use the "Sign in" button in the menu and the same account on both desktop and the mobile app. A page you left half-read on your phone opens right where you stopped.
Adjust the width and settle in
Grab the inner edge of the sidebar with the mouse and drag to resize it; keep it narrow and you will see only site icons. Reaching for the old top tab strip for the first few days is normal. Give it a week, and if it never clicks, the same setting turns it off in one click.
Tips
Watch out
When you send page content to the AI bot in the sidebar, that data goes to the servers of the service you picked. Avoid the summarise feature on pages holding personal information such as bank statements, government portal printouts or medical reports, because Firefox does not process this content locally.
Frequently asked questions
+How do I check which Firefox version I have?
The version number is listed in Menu > Help > About Firefox. If it is below 136, the update starts in that same window.
+Do I have to pay to use the AI bot?
Firefox charges nothing extra. If your chosen service has a free plan you use that; if it only offers paid access, you subscribe to that service.
+Will my tabs disappear if I turn vertical tabs off?
No. Clearing the option moves your open tabs back to the top strip as before, and nothing gets closed.
+Can I move the sidebar to the right side?
Yes, you can change the sidebar position to the right under Settings > General > Browser Layout.
+Why don't my phone tabs show up?
Make sure you are signed in with the same Mozilla account on both desktop and phone, and that "Open tabs" is ticked in the sync settings.
Sources and verification
Last verified: 13 Eylül 2026. tell us.
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