ACB File

What are ACB files and how to open them

Are you having problems opening an ACB 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 ACB files.

What is an ACB file?

ACB files have multiple uses, and Adobe Photoshop Color Book is one of them. Read more about the other uses further down the page.

Adobe Photoshop Color Book

These ACB files contain the colors used in Adobe Photoshop. Easily comply with color standards for printing an image versus using it on your computer, using this file. Adobe Photoshop uses ACB to load custom color books.

How to open ACB files

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

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

Last updated: August 16, 2026

All known file formats using extension .ACB

While Adobe Photoshop Color Book is a popular type of ACB-file, we know of 3 different uses of the .ACB file extension. Different software may use files with the same extension for different types of data.

Atom Cue Sheet Binary

Atom Cue Sheet Binary is a proprietary sound-data file used by the CRIWARE ADX2 system. It is produced by the authoring tool called CRI Atom Craft. The file bundles together cue definitions (the named sound events), parameter settings (pitch, volume, selectors, etc.), and any waveform audio data that must play from memory. It is used in games or interactive applications for triggering sounds via cues. Each .ACB file corresponds to one Cue Sheet.

When audio data in a Cue Sheet is flagged for streaming (i.e., not loaded wholly into memory), that streamed part is stored in a separate file with the .AWB extension; .ACB files contain only the parameters for streamed cues, not the streamed audio itself. All global project settings (categories, DSP buses, mixing, etc.) are stored in a single Atom Configuration File (.ACF), which .ACB refers to at runtime. Files are built per platform and per Cue Sheet. If a Cue Sheet is large (up to 65,535 cues), memory usage during loading increases; large projects often split Cue Sheets to manage resource usage.

For easy identification, .ACB files begin with the ASCII signature "@UTF" at offset 0. They contain internal markers and data-section keywords such as HEADER, FILEIDENTIFIER, VERSION, TYPE, MD5HASH, INDEX, VALUE, among others, which form recognizable labels in the file's internal structure.

AutoCAD Color Book

The AutoCAD Color Book format (file extension .acb) defines named sets of colors (called color books) in XML, used within AutoCAD-based software. These files let users collect and organize colors into "pages" of up to ten RGB colors each. Once a color book file is created or obtained, it's copied into a folder path registered in the software's Color Book Locations settings so that the colors appear in the Color Books tab inside color pickers.

These files are UTF-8 encoded XML documents that AutoCAD, Revit, or similar Autodesk products read. A user (or third party) writes one manually or via Autodesk's Color Book Editor. After saving, the software loads the .acb files from designated folders, and users can select individual pages and colors from the books to apply to layers, objects, hatches, backgrounds, and more.

Internally, the XML starts with an XML declaration ("<?xml version="1.0" encoding="UTF-8"?>") followed by a root element named colorBook. Key child elements include bookName, majorVersion, minorVersion, one or more colorPage elements, each with a pageColor (representative color) and up to ten colorEntry elements. Each color uses RGB8 format: red, green, blue values from 0 to 255. Some tags are case sensitive, and color names must be unique within the book.

Various apps that use files with this extension

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

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