If you use the same laptop for work and personal browsing, there's a default configuration problem: your work browsing and personal browsing share the same cookies, history, and session state.
This matters practically:
- Your work Slack and personal Slack can't be open simultaneously
- Your work Google account and personal Google account fight for the login session
- Work-related advertising follows you into personal browsing (and vice versa)
- A work security scan could technically see your full browsing history
Here are three approaches, from simplest to most thorough.
Approach 1: Firefox Profiles (Built-In)
Firefox supports multiple profiles with completely separate settings, extensions, and session state. Think of each profile as a completely separate Firefox installation.
Creating a second profile: type about:profiles in the address bar → "Create a New Profile." Give it a name like "Work."
Opening a specific profile: from the terminal, firefox -P "Work" or from the application menu. On macOS, right-click the Firefox dock icon → "New Window" can open a profile picker if you configure it.
Limitation: profiles can't be open simultaneously by default. You have to switch between them.
Workaround: Launch the second profile in a new instance with firefox --no-remote -P "Work". Both profiles run as separate processes.
Approach 2: Multi-Account Containers (More Practical)
The Multi-Account Containers extension is usually more practical than full profiles for work/personal separation:
- Both work and personal sessions run in the same Firefox window
- You can switch between them instantly
- You can assign sites to always open in specific containers (your work Google Apps domain opens in "Work" automatically)
Setup: Create a "Work" container. Assign your work tools to it (notion.so, slack.com, your company's GSuite domain). Personal sites go in the default container.
The work/personal separation is then automatic — you never have to think about which container to use.
Approach 3: Full Profile Separation for Maximum Isolation
For the strongest separation: use Firefox Profiles for work and personal, run them as separate processes, and use separate extension sets for each.
Work profile: minimal extensions, ETP set to "Standard" (less likely to break SSO flows), synced to a work Firefox Account.
Personal profile: privacy-focused extensions, ETP set to "Strict", synced to a personal Firefox Account.
This is the most setup, but gives complete separation: work cookies can never reach personal sites and vice versa, work IT can't see personal browsing history, and each profile maintains its own extension state.
What About Private Windows?
Private windows are often misunderstood as "work/personal separation." They're not. Private windows:
- Don't save history or cookies after the window closes
- Don't provide isolation from your current session while the window is open
- Share your IP address and browser fingerprint with sites
Private windows are useful for one-off tasks (logging in as someone else to test something, reading a paywalled article with a fresh cookie state). They're not a substitute for container-based or profile-based work/personal separation.
The New Tab in a Multi-Profile Setup
If you use full Firefox Profiles, you can set a different new tab for each profile. Work profile might use a minimal blank new tab (you're focused on work). Personal profile might use Weather & Clock Dashboard for the ambient weather and world clock context.
Each profile maintains its own extension preferences, so this configuration works per-profile.
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