Shiftr

Profile switcher for Firefox — quickly switch, create, rename, and manage your Firefox profiles from a single popup.

Install from AMO

Works with the legacy profile system (about:profiles), not the newer about:profilemanager.

Screenshots

  

Features

• Switch profiles — Click a profile to launch it in a new Firefox window
• Keyboard shortcut — Alt+Shift+P opens the Shiftr popup
• Quick switch — Inside the popup, press 1, 2, 3... to jump to a profile by number
• Create profiles — Create new profiles directly from the popup without leaving your browser
• Rename profiles — Click the three-dot menu on any profile to rename it
• Set default — Mark any profile as the default via the context menu
• Manage profiles — Quick link to open about:profiles for advanced management
• 6 themes — Cycle through Ayu (Dark, Mirage, Light) and Tokyo Night (Night, Storm, Light) with a single click. Theme choice is persisted across sessions.

How it works

Firefox extensions can't read the filesystem directly, so Shiftr uses Firefox's Native Messaging API. A small Python script (shiftr_host.py) reads profiles.ini, creates/renames profiles, and launches Firefox with the selected profile via firefox -P <name> -no-remote.

Prerequisites

• Firefox 109+
• Python 3.6+ — Check with python3 --version
• macOS or Linux (Windows support is partial — the Python host has Windows paths but the install script only supports macOS/Linux)

Installation

Step 1: Clone the repository

git clone <repo-url> shiftr
cd shiftr

Step 2: Install the native messaging host

./install.sh

This does two things:

1. Makes native-host/shiftr_host.py executable
2. Writes a manifest file to Firefox's native messaging hosts directory:
   • macOS: ~/Library/Application Support/Mozilla/NativeMessagingHosts/
   • Linux: ~/.mozilla/native-messaging-hosts/

The manifest tells Firefox where to find the Python script and which extension is allowed to use it.

Step 3: Load the extension in Firefox

Since this is an unsigned extension, load it as a temporary add-on:

1. Open Firefox
2. Go to about:debugging#/runtime/this-firefox
3. Click Load Temporary Add-on...
4. Navigate to the extension/ folder and select manifest.json

The Shiftr icon (swap arrows) will appear in your toolbar.

Note: Temporary add-ons are removed when Firefox restarts. You'll need to reload it each time. See Permanent Installation below to avoid this.

Step 4: Verify it works

1. Click the Shiftr icon in the toolbar — you should see your profiles listed
2. Click a profile name to launch Firefox with that profile
3. Try the keyboard shortcut Alt+Shift+P to open the popup
4. Click the palette icon in the header to cycle through themes

Usage

Action	How
Open Shiftr	Click toolbar icon or press Alt+Shift+P
Switch to a profile	Click the profile name in the popup
Quick switch by number	Press 1 for first profile, 2 for second, etc.
Create a new profile	Click + New Profile, type a name, press Enter or click Create
Rename a profile	Click the ⋮ menu on a profile → Rename
Set default profile	Click the ⋮ menu → Set as Default
Open about:profiles	Click Manage Profiles at the bottom of the popup
Change theme	Click the palette icon in the top-right corner of the popup

The default profile is highlighted and labelled "default" in the popup.

Themes

Six built-in themes, cycled with the palette button:

Theme	Style
Ayu Dark	Deep dark, warm gold accent
Ayu Mirage	Blue-grey dark, bright gold accent
Ayu Light	Clean white, orange accent
Tokyo Night	Indigo dark, blue accent
Tokyo Storm	Lighter indigo, blue accent
Tokyo Night Light	Cool grey light, deep blue accent

Your theme choice is saved and persists across popup opens and browser restarts.

Building

To build a distributable .zip:

cd extension
npx web-ext build

The output will be at extension/web-ext-artifacts/shiftr-1.0.0.zip.

To lint the extension for AMO compliance:

cd extension
npx web-ext lint

Permanent Installation

Temporary add-ons are fine for testing but get removed on restart. To install permanently:

Option A: Use web-ext for development

cd extension
npx web-ext run

This launches Firefox with the extension auto-loaded and auto-reloaded on file changes.

Option B: Sign and distribute

Sign via Mozilla's Add-on Developer Hub:

cd extension
npx web-ext sign --api-key=YOUR_KEY --api-secret=YOUR_SECRET

Or submit to addons.mozilla.org for public distribution.

Note: Even with a signed extension, you still need to run ./install.sh on each machine to register the native messaging host.

Customising the keyboard shortcut

If Alt+Shift+P conflicts with another extension or tool, you can change it in Firefox:

1. Go to about:addons
2. Click the gear icon (top right) and select Manage Extension Shortcuts
3. Find Shiftr and set your preferred shortcut

Troubleshooting

"Cannot connect to native host" error

• Make sure you ran ./install.sh first
• Verify the manifest exists:
  • macOS: cat ~/Library/Application\ Support/Mozilla/NativeMessagingHosts/shiftr_host.json
  • Linux: cat ~/.mozilla/native-messaging-hosts/shiftr_host.json
• Check that the "path" in the manifest points to the correct absolute path of shiftr_host.py
• Ensure Python 3 is available: python3 --version

No profiles listed

• Shiftr reads from profiles.ini, which is managed by about:profiles (the legacy system)
• If you created profiles using the newer about:profilemanager, they won't appear here
• Verify your legacy profiles exist: open about:profiles in Firefox
• Check that profiles.ini is readable:
  • macOS: cat ~/Library/Application\ Support/Firefox/profiles.ini
  • Linux: cat ~/.mozilla/firefox/profiles.ini

Profile launches but opens a new window in the same profile

• This can happen if Firefox is already running that profile. The -no-remote flag should handle this, but if it doesn't, close the target profile's window first.

Create profile fails or times out

• Firefox must be findable at the expected path:
  • macOS: /Applications/Firefox.app
  • Linux: firefox on PATH
• Profile names may only contain letters, numbers, spaces, hyphens, underscores, and dots

about:profiles vs about:profilemanager

Firefox has two profile systems:

• about:profiles (legacy) — Profiles stored in profiles.ini. This is what Shiftr reads and manages. Profiles created here are independent Firefox instances with separate bookmarks, history, extensions, etc.
• about:profilemanager (new) — A newer profile system introduced in recent Firefox versions with a different UI and storage mechanism. Shiftr does not support these profiles.

If you're unsure which system you use, open about:profiles in Firefox. If you see your profiles listed there, Shiftr will work for you.

Project structure

shiftr/
├── extension/
│   ├── manifest.json          # Extension manifest (permissions, shortcut, metadata)
│   ├── background.js          # Listens for keyboard shortcut, opens popup
│   ├── popup/
│   │   ├── popup.html         # Popup UI shell
│   │   ├── popup.css          # 6 theme definitions + base styles using CSS variables
│   │   └── popup.js           # Profile listing, switching, creation, renaming, theming
│   └── icons/
│       ├── icon-48.svg        # Toolbar icon (white swap arrows, transparent bg)
│       ├── icon-96.svg        # High-DPI toolbar icon
│       ├── icon-ext-48.svg    # Extensions page icon (dark bg)
│       └── icon-ext-96.svg    # High-DPI extensions page icon
├── native-host/
│   ├── shiftr_host.py         # Native messaging host (reads/writes profiles.ini)
│   └── shiftr_host.json       # Manifest template (install.sh generates the real one)
├── install.sh                 # Registers native messaging host with Firefox
├── LICENSE                    # MIT License
└── README.md

License

MIT