What is an ACT File?

How to Open, Edit, & Convert ACT Files

Screenshot of an ACT file icon used by Adobe Photoshop
The Adobe Color Table File Icon.

A file with the ACT file extension is an Adobe Color Table file (also called a Color Lookup Table file) used by Adobe Photoshop to store a collection of predefined colors. When saving an image for web publishing, you can add or eliminate colors to favor a higher quality image or a lower file size.

If it's not used with Photoshop, you may instead have an ADPCM Compressed Audio file. These ACT files are audio files used by some MP3 players and voice recorders that compress the audio file using Adaptive Differential Pulse Code Modulation.

Alma CAD/CAM Document files use the ACT file extension too. These files store instructions that 3D cutting machines use to understand how something should be cut.

An ACT file may instead be a Genesis3D Actor file, a DS Game Maker Action file, or a FoxPro Documenting Wizard Action Diagram file.

How To Open an ACT File

Adobe Color Table files can be opened with Adobe Photoshop, but you can't just double-click the file and have it open with Photoshop. Instead, you must import the ACT file into a specific window within the program. Several presets are already included in Photoshop's installation directory, in \Presets\en_US\Save for Web Settings\Color Tables\.

Start by opening the image you want to apply the ACT file to. Use Photoshop's File > Save for Web... menu to open the screen that you'll use to import the ACT file. Then, tap or click the small menu button on the top right corner of the "Color Table" section.

In that menu, choose Load Color Table... to browse for the ACT file you want to open.

Tip: This menu is also where you create an ACT file to save the settings for later use. Just pick the Save Color Table... if you want to do that.

You should also be able to open an Adobe Color Table file with Adobe Illustrator.

ADPCM Compressed Audio files will open with Konvertor, a Windows file manager that opens all sorts of file types, including not only audio files but also videos, archives, images, and more.

ACT files that are Alma CAD/CAM Document files can be opened with Alma act/cut 3D, Alma act/weld, and Alma act/tubes.

Genesis3D Actor files are 3D characters created with Genesis3D. That program can open these types of ACT files, but so should Autodesk's 3ds Max and chUmbaLum sOft's MilkShape 3D.

If your ACT file is instead a DS Game Maker Action file, it's supposed to open with Invisionsoft's DS Game Maker but unfortunately I can't find a download link for it. The file is used to store a game action like playing sounds or showing graphics. They're typically stored with ACTX files, which serve as a description for the action.

Microsoft Visual FoxPro is used to open FoxPro Documenting Wizard Action Diagram files.

Considering the number of formats that the ACT extension is used for, and the long list of programs that open those formats, you may very well find that one program you have installed is the default "open" program for files that end in ACT but you'd rather another program be. If that's the case, see How to Change File Associations in Windows for help changing it.

How To Convert an ACT File

I have no doubt that ACT files used with Photoshop can not be converted to any other format, but I'm sure the other file formats above can be saved to new formats, you just probably can't use a file converter to do it.

What I mean by this is that if the file can be converted, each specific program is likely capable of converting their own ACT file to a new format. For example, Konvertor should be able to save an ACT audio file to a more common audio format like MP3 or WAV.

Usually, if a program is able to convert a file to some other format, it's done through the File > Save As menu or some type of Export or Convert menu.