ADP File

What are ADP files and how to open them

Are you having problems opening an ADP 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 ADP files.

What is an ADP file?

ADP files have multiple uses, and Archimedes Protected Disk Image is one of them. Read more about the other uses further down the page.

Archimedes Protected Disk Image

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 ADP files

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

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

Last updated: August 17, 2026

All known file formats using extension .ADP

While Archimedes Protected Disk Image is a popular type of ADP-file, we know of 4 different uses of the .ADP file extension. Different software may use files with the same extension for different types of data.

Microsoft Access Project

These ADP files are Access Project files, files that give you a direct connection to a Microsoft SQL Server database through the OLE DB component architecture. With Microsoft Access Project, you create forms, reports, macros, and modules, just like a typical Access database. Access projects do not contain data or data-definition-based objects; their objects are in a SQL Server database.

Qt Assistant Documentation Profile

A Qt Assistant Documentation Profile is an XML-based configuration file used by the Qt Assistant help tool to define a custom documentation set. It allows developers to package HTML content together with metadata so that Qt Assistant can present the docs with a tailored title, icon, start page, and "About" information, among other display settings.

These profile files are created when building help for Qt applications or tools and are used by running Qt Assistant with the -profile filename.adp command‐line option. The .adp file extends the .dcf (Documentation Content File) format by including a <profile> section with <property> entries for things like name, title, application icon, startup page, "about" menu text, about dialog URL, and the location of the associated HTML documentation.

Technically, .adp files begin as XML files whose root is <assistantconfig version="3.2.0">. They include <profile> and one or more <DCF> elements. Property names like name, title, applicationicon, startpage, aboutmenutext, abouturl, assistantdocs appear inside <profile>. Under <DCF>, tags such as ref, icon, title, <section> and <keyword> define the documentation structure. The file often contains strings such as "ASSISTANTCONFIG VERSION", "PROPERTY NAME", "STARTPAGE", and "DCF REF" which act as internal identifiers.

Xilam DERF Audio

Xilam DERF Audio files store audio data used in video games by Xilam Animation. These files contain sound effects or background music encoded using a simple compressed format. They are created when a game by Xilam needs compact, low-resolution audio tracks that loop or play dynamically during gameplay. DERF Audio files are not standard music files - they are intended for internal use within those games.

DERF Audio files are produced by tools used during the game-asset creation process at Xilam Animation. They are decoded and played by the game engine on the fly rather than edited manually by end users. Because the audio is stored in compressed form, converting it back to standard PCM (uncompressed) can be done by specialized tools or converters meant to handle Xilam's DERF format.

Audio format uses DPCM compression: every "delta" byte modifies the previous sample to recreate waveform changes. The sampling frequency is fixed at 22,050 Hz. Channels can be mono or stereo; in stereo the delta bytes for both channels are interleaved. The delta byte encodes both sign (top bit) and magnitude via an index into a pre-defined delta table. Files start with the ASCII header DERF ("bytes 0-3: DERF"), followed by a 32-bit little-endian channel count, a 32-bit data size, then the sequence of delta bytes.

Various apps that use files with this extension

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