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Connect an extension to a desktop app

Some extensions talk to an app on your computer. A password manager’s extension, for example, asks its desktop app to unlock with Touch ID or Windows Hello. The app makes this possible by installing a small file, called a native messaging manifest, where the browser looks for it.

Sval reads these files from its own folders, and never from the folders Firefox uses. An app that only sets itself up for Firefox can’t reach Sval until you copy its file.

Your password manager’s extension in Sval says it can’t find the desktop app, though the app is running.

Find the app’s file

Section titled “Find the app’s file”

The app’s installer puts the file where Firefox reads it. The file is named after the app, such as com.8bit.bitwarden.json.

  • macOS: ~/Library/Application Support/Mozilla/NativeMessagingHosts
  • Linux: ~/.mozilla/native-messaging-hosts
  • Windows: In Registry Editor, go to HKEY_CURRENT_USER\Software\Mozilla\NativeMessagingHosts. Each key there is named after an app, and its default value is the path to the file.

Some apps install the file only when Firefox is on the computer. If you can’t find it, check the app’s own help for what the file holds.

Copy it to Sval

Section titled “Copy it to Sval”

Create the folder if it doesn’t exist.

  • macOS: Copy the file to ~/Library/Application Support/Sval/NativeMessagingHosts.
  • Linux: Copy the file to ~/.sval/native-messaging-hosts.
  • Windows: In Registry Editor, create the key HKEY_CURRENT_USER\Software\Sval\NativeMessagingHosts\<name>, with the same name as the key under Mozilla. Set its default value to the path of the file. It can be the same file Firefox uses.

The extension finds the app the next time it connects.

Details

Section titled “Details”
  • To set up a file for every user of a computer, use /Library/Application Support/Sval/NativeMessagingHosts on macOS, /etc/sval/native-messaging-hosts on Linux, or HKEY_LOCAL_MACHINE\Software\Sval\NativeMessagingHosts\<name> on Windows.
  • Sval reads managed storage files and security module files from the same places, under ManagedStorage and PKCS11Modules in place of NativeMessagingHosts (managed-storage and pkcs11-modules on Linux).
Section titled “Related pages”

© 2026 Ellm Tree, Inc. Sval is not officially associated with Mozilla or its products. Firefox is a trademark of the Mozilla Foundation in the US and other countries.