1. Signing is required via a compile-time flag for official builds of Firefox and Firefox Beta.
2. Signing is optional in other builds of Firefox (Unbranded, Developer Edition, and Nightly), and follows the `xpinstall.signatures.required` user preference.
3. On Linux, add-ons installed in `/usr/{lib,share}/mozilla/extensions` are exempt from signing.
4. Add-ons manually loaded via "Load Temporary Add-on" in about:debugging are also exempt from signing.
1. Signing is required via a compile-time flag for official builds of Firefox and Firefox Beta.
2. Signing is optional in other builds of Firefox (Unbranded, Developer Edition, and Nightly), and follows the `xpinstall.signatures.required` user preference.
3. On Linux, add-ons installed in `/usr/{lib,share}/mozilla/extensions` are exempt from signing.
4. Add-ons manually loaded via "Load Temporary Add-on" in about:debugging are also exempt from signing.