ADD File

What are ADD files and how to open them

Are you having problems opening an ADD 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 ADD files.

What is an ADD file?

ADD files have multiple uses, and AdLib Music is one of them. Read more about the other uses further down the page.

AdLib Music

We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

How to open ADD files

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

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

Last updated: August 17, 2026

All known file formats using extension .ADD

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

After Dark For DOS Module

After Dark For DOS Module files are screensaver modules designed to be loaded by the DOS version of After Dark, a screensaver program originally created by Berkeley Systems. These files store the logic, graphics, animations, sound cues, and configuration needed to display a specific screensaver effect when the system is idle. Each module defines how and when to animate, any user-configurable parameters, and what resources (images, sounds, palettes) it uses.

These .ADD files are produced by module developers using the After Dark Software Development Kit (SDK) published by Berkeley Systems, especially for version 3.0 modules adapted for DOS. Users don't manually write .ADD modules; instead, they are packaged by the SDK, then deployed so that the main After Dark DOS executable notices them when a module is selected. The After Dark engine reads/(executes) these files at idle time to show the effect, returning to DOS when activity resumes.

The format begins with a fixed ASCII signature "AD-DOSData." at file offset zero, followed by carriage return, line feed, and the DOS end-of-file control character 0x1A. The file also contains the strings "MODULE" and "ERROR" used internally for module identification or metadata.

Various apps that use files with this extension

These apps are known to open certain types of ADD files. Remember, different programs may use ADD 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 ADD file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.