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 78, Firefox ESR 78
CCK2 Equivalent: N/A
Preferences Affected: N/A

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"
      }]
    }
  }
}

Windows (Intune)

OMA-URI:

./Device/Vendor/MSFT/Policy/Config/Firefox~Policy~firefox/Handlers

Value (string):

<enabled/>
<data id="Handlers" value='
{
  "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&amp;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"
      }]
    }
  }
}
'/>

If you are using custom ADMX and ADML administrative templates in Intune, you can use this OMA-URI instead to workaround the limit on the length of strings. Put all of your JSON on one line.

OMA-URI:

./Device/Vendor/MSFT/Policy/Config/Firefox~Policy~firefox/HandlersOneLine

Value (string):

<enabled/>
<data id="JSONOneLine" value='{}'/>

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>

policies.json

{
  "policies": {
    "Handlers": {
      "mimeTypes": {
        "application/msword": {
          "action": "useSystemDefault",
          "ask": 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": "/usr/bin/acroread"
          }]
        }
      }
    }
  }
}