Type Object
Mandatory Usually, no (but see also When do you need an Add-on ID?). Mandatory before Firefox 48 (desktop) and Firefox for Android.
"applications": {
  "gecko": {
    "id": "addon@example.com",
    "strict_min_version": "42.0"


The applications key contains keys that are specific to a particular host application.

Firefox (Gecko) properties

Currently this contains just one key, gecko, which may contain four string attributes:

  • id is the extension ID. Optional from Firefox 48, mandatory before Firefox 48. See Extensions and the Add-on ID to see when you need to specify an add-on ID.
  • strict_min_version: minimum version of Gecko to support. Versions containing a "*" are not valid in this field. Defaults to "42a1".
  • strict_max_version: maximum version of Gecko to support. If the Firefox version on which the extension is being installed or run is above this version, then the extension will be disabled, or not permitted to be installed. Defaults to "*", which disables checking for a maximum version.
  • update_url is a link to an extension update manifest. Note that the link must begin with "https". This key is for managing extension updates yourself (i.e. not through AMO).

See the list of valid Gecko versions.

Extension ID format

The extension ID must be one of the following:

  • GUID
  • A string formatted like an email address: extensionname@example.org

The latter format is easier to generate and manipulate. Be aware that using a real email address here may attract spam.

For example:

"id": "extensionname@example.org",

"id": "{daf44bf7-a45e-4450-979c-91cf07434c3d}"

Microsoft Edge properties

Microsoft Edge stores its browser specific settings in the edge subkey, which has the following properties:


Boolean property which controls the placement of the browser action.


Example with all possible keys. Note that most extensions will omit strict_max_version and update_url.

"applications": {
  "gecko": {
    "id": "addon@example.com",
    "strict_min_version": "42.0",
    "strict_max_version": "50.*",
    "update_url": "https://example.com/updates.json"
  "edge": {
    "browser_action_next_to_addressbar": true

Browser compatibility

ChromeEdgeFirefoxFirefox for AndroidOpera
Basic support No151






1. Supported as browser_specific_settings.

Document Tags and Contributors

Last updated by: hellosct1,