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SyncTabs — Cross-Browser Tab Sync

See and switch to every open tab across all your Chromium browsers — from one place, in real time.

Version MV3 Platforms Browsers

What It Does

Install SyncTabs in every Chromium browser you use. The popup instantly shows:

  • Your current browser's tabs — all windows, all tabs, with favicons
  • Every other browser's tabs — grouped by browser name
  • Tabs from closed browsers — their last session is always visible
  • One click on any remote tab opens it in your current browser

No account. No subscription. The current release line is local-first and keeps sync on your own machine.

Two Modes

Feature Local Mode (default, zero setup) Sync Mode (with Companion app)
View & switch your own tabs ✅ ✅
Tabs survive browser close ✅ ✅
Tabs grouped by window ✅ ✅
Active + pinned tab indicators ✅ ✅
See tabs from other browsers ❌ ✅
Real-time sync across browsers ❌ ✅
"Last seen" for offline browsers ❌ ✅
Click to open remote tab here ❌ ✅

Quick Start

Step 1 — Install the Extension (in each browser)

From browser stores (recommended — auto-updates)

Browser Store
Google Chrome Chrome Web Store (coming soon)
Microsoft Edge Edge Add-ons (coming soon)
Brave / Vivaldi / Opera Use the Chrome Web Store link

Or sideload manually (no store needed):

  1. Download this repo → unzip
  2. Go to chrome://extensions in your browser
  3. Enable Developer mode (top-right toggle)
  4. Click Load unpacked → select the extension/ folder
  5. Pin the SyncTabs icon to your toolbar

Repeat in every browser where you want tabs visible.

Step 2 — Install the Companion App (for cross-browser sync)

The Companion is a lightweight background app (~10 MB). It runs a local WebSocket server on 127.0.0.1 (default port 9234, configurable to another localhost port). It never connects to the internet.

Download from GitHub Releases:

Platform File
Windows synctabs-companion-windows-amd64.exe
macOS (Apple Silicon) synctabs-companion-darwin-arm64
macOS (Intel) synctabs-companion-darwin-amd64
Linux (x64) synctabs-companion-linux-amd64
Linux (.deb) synctabs-companion_<version>_amd64.deb

Windows

  1. Download synctabs-companion-windows-amd64.exe
  2. Double-click to run — a tray icon appears in your taskbar
  3. Right-click the tray icon → Start with Windows to auto-start on login

Windows may show a SmartScreen warning on first run (unsigned binary). Click More info → Run anyway.

macOS

# Make executable
chmod +x synctabs-companion-darwin-arm64

# Remove quarantine (required for unsigned apps)
xattr -d com.apple.quarantine synctabs-companion-darwin-arm64

# Run
./synctabs-companion-darwin-arm64

A tray icon appears in your menu bar. Right-click → Start with Login to auto-start.

Linux

# Option A: .deb package (Ubuntu/Debian)
sudo dpkg -i synctabs-companion_<version>_amd64.deb
synctabs-companion &

# Option B: Binary
chmod +x synctabs-companion-linux-amd64
./synctabs-companion-linux-amd64 &

Alternative: Run Dev Server (for development)

If you're working on the extension or companion code, you can run the Node.js development server instead:

Requires Node.js 24 LTS.

# Windows
start-server.bat

# macOS / Linux
./start-server.sh

This will:

  1. Check for Node.js installation
  2. Install dependencies (npm install)
  3. Start the server on localhost:9234

Press Ctrl+C to stop.

Note: The dev server is only for local development. Production builds and release artifacts come from the Go companion app, not from packaged Node binaries.

Step 3 — Grant Permission (one-time, per browser)

The extension needs permission to talk to 127.0.0.1:

  1. Click the SyncTabs icon → open popup
  2. Click Settings (gear icon)
  3. Click Grant localhost permission
  4. Confirm in the browser prompt

The extension auto-detects the Companion within a few seconds. The status dot turns green.

Platform Notes

Chromebook / ChromeOS

  • The extension works in Local Mode on Chromebook.
  • Sync Mode is not currently supported as a normal Chromebook install path, because there is no ChromeOS companion build in this repo.
  • Some Linux-enabled Chromebooks may be able to run the Linux companion experimentally, but that is not an officially supported setup.
  • A Chromebook-friendly sync option is planned for a future release line.

Using SyncTabs

Popup

Click the toolbar icon to open it.

  • Header — your browser name · connection status dot (🟢 syncing · 🟡 offline/cached · ⚫ local only)
  • This Browser — your current windows and tabs (collapsible)
  • Remote Browsers — one card per other browser, with online/offline badge + last-seen time
  • Click any remote tab to open it here
  • Hover a remote tab for a Send Tab button (pushes it to that browser)

Tray Icon (Companion)

Right-click the tray icon for:

Menu Item Action
Status Live count of connected browsers
Open Data Folder Browse saved tab data
View Logs Open log file in Notepad
Restart Server Restart the WebSocket server
Start with Windows Toggle auto-start on login
Settings... Note: configure via extension options
Quit Stop the Companion

Settings (Extension)

Open via gear icon in the popup, or right-click toolbar icon → Options.

  • Enable / disable sync
  • Server URL (default ws://127.0.0.1:9234, customizable to another localhost port)
  • Grant localhost permission
  • Test Connection
  • Clear cached remote tab data

How It Works

 Browser A (Chrome)          SyncTabs Companion           Browser B (Edge)
 ┌─────────────────┐         ┌──────────────────┐         ┌─────────────────┐
 │  Extension      │◄───WS───│  127.0.0.1:<port> │───WS───►│  Extension      │
 │  (background.js)│         │                  │         │  (background.js)│
 └─────────────────┘         │  tabs.json       │         └─────────────────┘
                              │  (persists last  │
 Browser C (Brave)            │   session even   │
 ┌─────────────────┐         │   when closed)   │
 │  Extension      │◄───WS───│                  │
 └─────────────────┘         └──────────────────┘
  • Each browser extension maintains a WebSocket connection to the Companion
  • Tab changes are pushed in real-time to all other connected browsers
  • The Companion persists tab data so closed-browser sessions remain visible
  • Everything is 127.0.0.1 only — nothing leaves your machine
  • The extension only accepts ws://127.0.0.1:<port> server URLs for the current release line

Privacy & Permissions

Permission Why
tabs Read your open tabs to display them
storage Save tab snapshots locally
alarms Periodic heartbeat to stay connected
http://127.0.0.1/* Optional — only when sync is enabled

Full details: PRIVACY.md

Troubleshooting

Status dot is grey (LOCAL mode) No Companion running. Install and start it, then grant localhost permission in the extension settings.

Status dot is yellow (offline/cached) Companion was detected before but is not running now. Start the Companion and click Test Connection in settings.

Companion shows SmartScreen warning (Windows) The binary is unsigned. Click More info → Run anyway. The source code is fully public for review.

Extension shows wrong browser name (e.g. "Google Chrome" for Brave) Browser detection uses the user-agent. Some browsers hide their identity. Each browser still has a unique ID and syncs correctly.

Port already in use Another app is using the selected localhost port. Edit %APPDATA%\SyncTabs\config.json and change the port value. Set the same value in extension Settings → Server URL.

Tabs not updating in real time Chromium service workers can be suspended when idle. The extension reconnects automatically. If tabs seem stale, click the refresh button in the popup.

Can I use this on a Chromebook? The extension works in local-only mode. Cross-browser sync on Chromebook is not officially supported yet because there is no ChromeOS companion build.

Data & Storage

The Companion stores data at:

Platform Path
Windows %APPDATA%\SyncTabs\data\
macOS ~/Library/Application Support/SyncTabs/data/
Linux ~/.local/share/SyncTabs/data/

Files:

  • tabs.json — last known tabs for each browser
  • pending-tabs.json — tabs queued for offline delivery
  • synctabs-companion.log — application log
  • ../config.json — port, log level, data folder, auto-start

Project Structure

Extension-synctabs/
├── extension/              # Browser extension (all browsers)
│   ├── manifest.json
│   ├── background.js       # Service worker: tab monitoring + WebSocket
│   ├── popup.html/js/css   # Main UI
│   ├── options.html/js     # Settings page
│   └── icons/
├── companion/              # Go companion app (replaces old Node.js server)
│   ├── main.go
│   ├── config/             # Config loading + persistence
│   ├── server/             # WebSocket + HTTP server
│   ├── tray/               # System tray icon + menu
│   ├── startup/            # OS auto-start registration
│   └── logger/
├── PRIVACY.md
└── README.md

Building from Source

Requires Go 1.21+.

cd companion

# Windows
GOOS=windows GOARCH=amd64 go build -ldflags "-H windowsgui" -o synctabs-companion-windows-amd64.exe .

# macOS (Apple Silicon)
GOOS=darwin GOARCH=arm64 go build -o synctabs-companion-darwin-arm64 .

# macOS (Intel)
GOOS=darwin GOARCH=amd64 go build -o synctabs-companion-darwin-amd64 .

# Linux
GOOS=linux GOARCH=amd64 go build -o synctabs-companion-linux-amd64 .

macOS and Linux builds require CGo and must be compiled on the target OS (or via GitHub Actions).

Roadmap

  • Keep the current release line local-first and store-compliant.
  • Add stronger localhost companion hardening.
  • Explore optional cloud sync and WebRTC relay modes for future releases.
  • Add a Chromebook-friendly sync path that does not depend on a native companion install.

License

MIT — see LICENSE

Developed by Harsh Vasudeva

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