# FF Session Importer > Import Firefox sessionstore files and open tabs in new windows Canonical page: [https://chrome-stats.com/d/ff-session-importer](https://chrome-stats.com/d/ff-session-importer) ## Overview - **ID:** `ff-session-importer` - **Platform:** Firefox - **Type:** Firefox add-on - **Status:** Available - **Publisher:** soyeb - **Category:** tabs - **Daily users:** 27 - **Weekly downloads:** 8 - **Version:** 1.0 - **Last updated:** 2026-02-03 - **First published:** 2026-02-02 - **Size:** 25 KB - **Data as of:** 2026-09-07 - **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/ff-session-importer/) - **Website:** [https://bitbucket.org/soyeb/firefox-session-importer/src/master/](https://bitbucket.org/soyeb/firefox-session-importer/src/master/) ## Description FF Session Importer for Firefox A Firefox extension that imports Firefox sessionstore files (.jsonlz4, .json, .baklz4) and opens the contained tabs in Firefox windows. Features

Import Firefox sessions: Load Firefox sessionstore files directly into Firefox
Multiple formats: Supports compressed (.jsonlz4, .baklz4) and uncompressed (.json) session files
Window preservation: Each Firefox window opens in a separate Firefox window
Simple interface: Just select a file and import

Installation From Firefox Web Store (Coming soon) Manual Installation (Developer Mode)

Download or clone this repository
Open Firefox and navigate to Firefox://extensions/
Enable "Developer mode" (toggle in top-right corner)
Click "Load unpacked"
Select the extension directory

Usage

Click the extension icon in Firefox's toolbar
Click "Choose File" or drag & drop a Firefox sessionstore file
sessionstore.jsonlz4 (current session)
recovery.jsonlz4 (crashed session)
previous.jsonlz4 (previous session)
Any .json session backup
Preview the loaded tabs and windows
Click "Import Tabs" to open all tabs in new Firefox windows

File Locations Firefox sessionstore files are typically located at:

Windows: %APPDATA%\Mozilla\Firefox\Profiles\[profile]\sessionstore.jsonlz4
macOS: ~/Library/Application Support/Firefox/Profiles/[profile]/sessionstore.jsonlz4
Linux: ~/.mozilla/firefox/[profile]/sessionstore.jsonlz4

How It Works

Decompresses .jsonlz4 files using LZ4 decompression
Parses Firefox's sessionstore JSON format
Extracts URLs from tabs and windows
Creates new Firefox windows with the extracted tabs

Privacy

All file processing happens locally in your browser
No data is sent to external servers
No tracking or analytics

Dependencies

LZ4 decompression: Uses a modified version of lz4js by John Chadwick

Development Building from Source No build process required. The extension uses vanilla JavaScript. Testing

Load the extension in developer mode
Use test sessionstore files from your Firefox profile

File Structure

firefox-session-importer/
└── Firefox/
  ├── lz4.js # LZ4 decompression library
  ├── manifest.json # Extension manifest
  ├── background.js # Background service worker
  ├── popup.html # Extension popup UI
  ├── popup.js # Popup functionality
  ├── styles.css # Popup styles
  ├── lib/
  │ └── lz4.js # LZ4 decompression library
  ├── icons/ # Extension icons
  ├── README.md # This file
  ├── LICENSE # ISC License
  └── CHANGELOG.md # Version history

Limitations

No form data/cookies: Only URLs are imported, not form data, cookies, or browsing history
Firefox-specific URLs: URLs starting with about:, Firefox:, or moz-extension: are skipped
Large sessions: Very large sessions may take time to import

Troubleshooting "Failed to decompress LZ4 file"

Ensure you're using a valid Firefox sessionstore file
Try using a different session file (recovery.jsonlz4, previous.jsonlz4)

"No valid URLs found"

The session file may be corrupted or empty
Try restoring from a different backup

Extension not loading

Ensure developer mode is enabled in Firefox://extensions/
Check Firefox console for errors (F12 → Console)

Contributing

Fork the repository
Create a feature branch
Make your changes
Submit a pull request

License ISC License - see LICENSE file for details. Acknowledgments

LZ4 decompression: Modified from lz4js by John Chadwick
Firefox session format: Reverse-engineered from Firefox source code

## Rankings - #21,532 — Overall - #23 — import - #45 — session - #87 — mission ## Permissions and access ### Permissions - `tabs` - `` ## Safety - **Risk impact:** High risk impact - **Risk likelihood:** Moderate risk likelihood ### Analysis details - Grants access to browser tabs, which can be used to track user browsing habits and history, presenting a privacy concern. - This extension has low user count. Unpopular extensions may not be stable or safe. > Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing). ## Similar extensions and apps - [Session Manager](https://chrome-stats.com/d/session-manager-latest) — 5 users - [Workflow Session Manager](https://chrome-stats.com/d/workflow-session-manager) — 6 users, 1.00 / 5 - [Session Importer](https://chrome-stats.com/d/session-importer) — 17 users - [Woob session importer](https://chrome-stats.com/d/woob-session-importer) — 6 users - [Browser Session Manager](https://chrome-stats.com/d/browser-session-manager-edit) — 7 users - [Tab Exporter/Importer](https://chrome-stats.com/d/tab-exporter-importer) — 28 users, 2.50 / 5 - [Daily Session Saver](https://chrome-stats.com/d/daily-session-saver) — 1 users - [Tabs Import](https://chrome-stats.com/d/tabs-import) — 273 users, 3.67 / 5 - [Tab Backup](https://chrome-stats.com/d/tab-backup) — 17 users - [Easy Session Manager](https://chrome-stats.com/d/easy-session-manager) — 428 users, 3.84 / 5 - [Session Switcher](https://chrome-stats.com/d/session-switcher) — 26 users, 5.00 / 5 - [Sessionic](https://chrome-stats.com/d/sessionic) — 197 users, 5.00 / 5 --- Source: [Chrome-Stats](https://chrome-stats.com/d/ff-session-importer)