Minifilter Altitude Request

A request for an minifilter altitude assignment is sent to Microsoft as an email. The body of the email must contain the following fields and corresponding information.

Field Comment
Company name:
Contact e-mail:
Product name:
Product URL:
Product/Filter description: A one paragraph summary to help Microsoft determine an appropriate altitude for the filter.
Filter filename:
Filter type: One of these values: Registry, FileSystem, Both
Filter start-type: One of these values: Boot, System, Auto, Demand
Requested filter load order group: See the File System Minifilter Allocated Altitudes for available load order groups.
Requested altitude: Microsoft reserves the right to assign an altitude that is different from the requested altitude, depending on altitude availability and the filter driver functionality.
Additional information: Use this field to let us know if there is any information you would like Microsoft to consider when assigning an altitude to this filter.

Send this information in an ASCII text e-mail message to with the subject: “Minifilter altitude request”. An altitude for this filter will then be e-mailed back to the specified contact e-mail address.

The following is an example for the body of an allocation request email.


Below is the request information to assign an altitude for our Contoso DataKleen file system minifilter.

Company name: Contoso Ltd.
Contact e-mail:
Product name: Contoso DataKleen
Product URL:
Product/Filter Description:
    The Contoso DataKleen filter removes all occurences of any byte having a value
    between 128 and 255 during file reads. Our minifilter removes this value since
    it is not displayable on TTY devices.
Filter filename: ContosoDK.sys
Filter type: FileSystem
Filter start-type: Demand
Requested filter load order group: FSFilter Content Screener
Requested altitude: 268400
Additional information: None




  • All fields must be filled out.
  • It may take Microsoft up to two weeks to process and assign altitudes. Any missing information may delay the assignment.
  • The assigned altitude will eventually be reflected in the altitudes listed in File System Minifilter Allocated Altitudes. Please be aware that Microsoft only updates this list annually.