How the Firefox Migration Wizard Imports Browser Data

Moving to a new web browser can seem daunting, especially when years of personal data are stored in your old one. This article provides a quick overview and breakdown of the technical process behind the Firefox Migration Wizard. It covers exactly how Firefox locates, translates, and transfers your bookmarks, browsing history, saved passwords, and extensions from browsers like Chrome, Edge, and Safari directly into your new Firefox profile.

Locating the Source Data

Every web browser stores your personal data locally on your computer inside specific hidden folders known as user profiles. When you launch the Firefox Migration Wizard, it automatically scans the default file paths on your operating system (Windows, macOS, or Linux) to detect installed browsers. Once you select which browser and profile to import from, Firefox reads the raw data files from that browser's local directory without altering or deleting the original files.

Bookmarks and Browsing History

Browsers store bookmarks and history in structured files, typically using SQLite databases or JSON (JavaScript Object Notation) files.

  • Reading the Data: For Chromium-based browsers (like Chrome, Edge, and Brave), bookmarks are stored in a JSON file, while history is kept in an SQLite database. Safari uses Property List (.plist) and SQLite files. The Migration Wizard opens these files in a read-only state.
  • Translating and Writing: Firefox uses a unified database called places.sqlite to manage both bookmarks and history. The wizard extracts the URLs, page titles, visit counts, timestamps, and folder structures from the old browser. It then converts this data into a format Firefox understands and writes it directly into the places.sqlite file.

Saved Passwords

Importing passwords requires an extra layer of security because browsers never store passwords in plain text.

  • Decryption: Browsers like Chrome and Edge encrypt your passwords using your operating system’s built-in security features—such as the Data Protection API (DPAPI) on Windows or the Keychain on macOS. Because you are running the Firefox Migration Wizard while logged into your own operating system account, Firefox has the necessary permissions to ask the operating system to decrypt the old browser's password database.
  • Re-encryption: Once the passwords and their associated website URLs and usernames are decrypted in the computer's temporary memory, Firefox immediately re-encrypts them using its own security architecture. The data is then safely stored inside your Firefox profile in files named logins.json and key4.db.

Extensions

Unlike bookmarks or passwords, browser extensions cannot simply be copied and pasted from one browser to another due to differences in browser architecture and security signing.

  • Identifying Extensions: The Migration Wizard looks into the old browser's "Extensions" folder to read the unique IDs of the extensions you have installed.
  • Matching and Downloading: Mozilla maintains a mapping list that links popular Chrome and Edge extension IDs to their exact counterparts on the Firefox Add-ons store. The wizard compares your installed extension IDs against this list. When it finds a match, Firefox connects to the internet, downloads the official Firefox version of that extension directly from Mozilla's servers, and installs it into your new browser. If an extension does not have a mapped equivalent, it is simply skipped.