HMK File

What are HMK files and how to open them

Are you having problems opening a HMK file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your HMK files.

What is a HMK file?

A .HMK file is a Hallmark Card Studio file.

Hallmark Card Studio File (extension .HMK) is a project file used by the Windows software Hallmark Card Studio for designing custom greeting cards. These files save card layouts that include text, formatting choices, and placeholders for images, but they do not embed all image or animation assets. They are the working file users edit while designing cards, invitations, letters,or similar printed or digital greeting items.

Hallmark Card Studio creates .HMK files when you start a new card project and save it. You reopen and modify them later using the same program. When you want to share the design with others or use outside the software, the project can usually be exported or printed from Hallmark Card Studio, possibly to formats like PDF or directly to a printer.

Technically, .HMK files use a compound document format with a recognizable signature: they begin with the Microsoft Compound File Binary signature (bytes D0 CF 11 E0 A1 B1 1A E1 at offset 0). Inside the file are identifiable strings such as "Root Entry" at offset 1024 and various GUIDs.

How to open HMK files

We have identified one HMK opener that is compatible with this specific type of HMK file.

Programs that open Hallmark Card Studio files

Last updated: August 7, 2026

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