CPO File

What are CPO files and how to open them

Are you having problems opening a CPO 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 CPO files.

What is a CPO file?

CPO files have multiple uses, and Compo Composition is one of them. Read more about the other uses further down the page.

Compo Composition

Compo Composition files store the working-state of a graphics document created in the RISC OS application Compo (also known as !Composition). They capture all editable elements such as layers, masks, effects, object positions and settings, so that work can be resumed later without loss of detail.

The Compo program saves these files when the user chooses to save a composition rather than exporting it. They are typically reloaded by the same application, allowing further editing - adding or moving objects, tweaking effects like shadows, masks, opacity, vector operations and so on. Compo also supports exporting its compositions in formats such as RISC OS sprites or JPEG once editing is complete.

Internally the file is a text-based format (often with binary data embedded for image and mask content, if the "with images and masks" option is enabled) that begins with the ASCII signature "#Composition #Saved:" at the very start of the file. It contains human-readable keywords like CANVAS BYTES_PER_PIXEL, EXPORT FILE FORMAT, THE BASE SCALE ON DPI, MULTI-TASK REDRAW, GRID OPTIONS, VIRTUAL MEMORY, PALETTE, LOCK, SHOW, SAVED, ASPECT, XSPACING, YSPACING, etc.

How to open CPO files

Important: Different programs may use files with the CPO file extension for different purposes, so unless you are sure which format your CPO file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested five different CPO openers which you will find listed below.

Last updated: September 18, 2026

All known file formats using extension .CPO

While Compo Composition is a popular type of CPO-file, we know of 2 different uses of the .CPO file extension. Different software may use files with the same extension for different types of data.

Corel Print Office Image

Corel Print Office Image files are used by Corel's home-publishing program formerly known as Corel Print House (also called Corel Print Office or Print House/Print Office). They store a whole design project - layouts composed of graphics, image data, clip art, and text - created when working on calendars, greeting cards, banners, scrapbooks or other printable domestic publishing jobs. Such files are intended for use inside the design app rather than as a standard image format for other programs.

Creation happens when a user saves or exports work inside Corel Print House / Print Office; the file format captures both the layout (positions, typography, objects) and embedded or linked image content. When reopening the file, Corel Print House reads this project file so the design remains editable: text remains as text, objects can be moved, styles and images preserved. These files are not aimed at professional printing interchange by themselves but serve as full-fidelity save states within that specific program.

Internally the file begins with the OLE Compound File signature 0xD0CF11E0A1B11AE1 at the start, and contains readable Unicode strings at specific offsets such as "ROOT ENTRY" near offset 1024, "THUMBNAIL", "HEADER", "CONTENTS" and "IMAGES", all of which help identify the file as a Corel Print Office Image document.

Various apps that use files with this extension

These apps are known to open certain types of CPO files. Remember, different programs may use CPO files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CPO file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.