ACS4 File

What are ACS4 files and how to open them

Are you having problems opening an ACS4 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 ACS4 files.

What is an ACS4 file?

An .ACS4 file is an AIMP Skin file.

A file with the .ACS4 extension is a compiled skin for AIMP version 4, the music player by Artem Izmaylov. It completely changes the visual design of the player (buttons, layout, color scheme, graphics) by replacing the default interface look. Such skins let users customize appearance without altering how AIMP functions.

These ACS4 files are created by the AIMP Skin Editor. You use the editor to design or assemble a theme, then export it into the ACS4 form. Once compiled into this format, the skin becomes read-only and cannot be edited through Skin Editor unless the original skin project file (with extension .ACS4proj) is available. ACS4 skins are meant for deployment and use, not modification.

When opened by AIMP (on Windows or Android), an ACS4 file is loaded as a resource package containing all the graphics, layout data, and styling instructions needed for rendering the customized interface. These compiled skins are efficient for runtime because much of the data is preprocessed.

At the binary level, every ACS4 skin file begins with the ASCII signature "ACS4" (hex 41 43 53 34) at offset zero.

How to open ACS4 files

Important: Different programs may use files with the ACS4 file extension for different purposes, so unless you are sure which format your ACS4 file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 17, 2026

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