Handlers

Configure default application handlers. This policy is based on the internal format of handlers.json.

You can configure handlers based on a mime type (mimeTypes), a file's extension (extensions), or a protocol (schemes).

Compatibility

Firefox	Firefox ESR	Firefox Enterprise
Available since 78	Available since 78	Available since 149

CCK2 Equivalent: N/A
OMA-URI: Handlers
Preferences Affected: N/A

Examples

policies.json

{
  "policies": {
    "Handlers": {
      "mimeTypes": {
        "application/msword": {
          "action": "useSystemDefault",
          "ask": false
        }
      },
      "schemes": {
        "mailto": {
          "action": "useHelperApp",
          "ask": true,
          "handlers": [
            {
              "name": "Gmail",
              "uriTemplate": "https://mail.google.com/mail/?extsrc=mailto&url=%s"
            }
          ]
        }
      },
      "extensions": {
        "pdf": {
          "action": "useHelperApp",
          "ask": true,
          "handlers": [
            {
              "name": "Adobe Acrobat",
              "path": "/usr/bin/acroread"
            }
          ]
        }
      }
    }
  }
}

JSON schema

Handlers JSON schema

{
  "type": "object",
  "contentMediaType": "application/json",
  "patternProperties": {
    "^(mimeTypes|extensions|schemes)$": {
      "type": "object",
      "patternProperties": {
        "^.*$": {
          "type": "object",
          "properties": {
            "action": {
              "type": "string",
              "enum": [
                "saveToDisk",
                "useHelperApp",
                "useSystemDefault"
              ]
            },
            "ask": {
              "type": "boolean"
            },
            "handlers": {
              "type": "array",
              "items": {
                "type": "object",
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "path": {
                    "type": "string"
                  },
                  "uriTemplate": {
                    "type": "string"
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

Values

Within each handler type, you specify the given mimeType/extension/scheme as a key and use the following subkeys to describe how it is handled.

Name	Description
action	Can be either saveToDisk, useHelperApp, useSystemDefault.
ask	If true, the user is asked if what they want to do with the file. If false, the action is taken without user intervention.
handlers	An array of handlers with the first one being the default. If you don't want to have a default handler, use an empty object for the first handler. Choose between path or uriTemplate.
name	The display name of the handler (might not be used).
path	The native path to the executable to be used.
uriTemplate	A url to a web based application handler. The URL must be https and contain a %s to be used for substitution.

Windows (GPO)

Software\Policies\Mozilla\Firefox\Handlers (REG_MULTI_SZ) =

{
  "mimeTypes": {
    "application/msword": {
      "action": "useSystemDefault",
      "ask": true | false
    }
  },
  "schemes": {
    "mailto": {
      "action": "useHelperApp",
      "ask": true | false,
      "handlers": [{
        "name": "Gmail",
        "uriTemplate": "https://mail.google.com/mail/?extsrc=mailto&url=%s"
      }]
    }
  },
  "extensions": {
    "pdf": {
      "action": "useHelperApp",
      "ask": true | false,
      "handlers": [{
        "name": "Adobe Acrobat",
        "path": "C:\\Program Files (x86)\\Adobe\\Acrobat Reader DC\\Reader\\AcroRd32.exe"
      }]
    }
  }
}

macOS

<dict>
  <key>Handlers</key>
  <dict>
    <key>mimeTypes</key>
    <dict>
      <key>application/msword</key>
      <dict>
        <key>action</key>
        <string>useSystemDefault</string>
        <key>ask</key>
        <true/> | <false/>
      </dict>
    </dict>
    <key>schemes</key>
    <dict>
      <key>mailto</key>
      <dict>
        <key>action</key>
        <string>useHelperApp</string>
        <key>ask</key>
        <true/> | <false/>
        <key>handlers</key>
        <array>
          <dict>
            <key>name</key>
            <string>Gmail</string>
            <key>uriTemplate</key>
            <string>https://mail.google.com/mail/?extsrc=mailto&url=%s</string>
          </dict>
        </array>
      </dict>
    </dict>
    <key>extensions</key>
    <dict>
      <key>pdf</key>
      <dict>
        <key>action</key>
        <string>useHelperApp</string>
        <key>ask</key>
        <true/> | <false/>
        <key>handlers</key>
        <array>
          <dict>
            <key>name</key>
            <string>Adobe Acrobat</string>
            <key>path</key>
            <string>/System/Applications/Preview.app</string>
          </dict>
        </array>
      </dict>
    </dict>
  </dict>
</dict>