What Is an ACT File?

Tim Fisher has more than 30 years' of professional technology experience. He's been writing about tech for more than two decades and serves as the SVP and General Manager of Lifewire.

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What to Know

• An ACT file could be an Adobe Color Table file used by Photoshop to store a collection of colors.
• Go to File >Save for Web, or File >Export >Save for Web (Legacy), to find the option to import the file.
• This file extension is also used by other software for storing audio, documents, and game data.

This article examines several file formats that use the ACT file extension. It explains what each file type is, how to open each kind, and how to convert your file to a different file format (if possible).

What Is an ACT File?

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 are used by some MP3 players and voice recorders that compress the audio using Adaptive Differential Pulse Code Modulation.

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

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

ACT is also the abbreviation for some tech terms that are unrelated to these file formats. Some examples include action tracking, automatic code translation, account contact tool, and access charge terminal.

How to Open an ACT File

Adobe Color Table files can be opened with Photoshop. Several presets are already included in the program's installation folder, but you can also import new ones:

1. Open the image you want to apply the ACT file to.

Select the small menu button in the top right corner of the Color Table section. In there, choose Load Color Table to browse for the ACT file.

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 documents can be opened with Almacam Space Cut, Almacam Weld, and Almacam Tube.

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 file is instead a DS Game Maker Action file, it's supposed to open with Invisionsoft's DS Game Maker but, unfortunately, we 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's discontinued Visual FoxPro is used to open FoxPro Documenting Wizard Action Diagram files.

Considering the number of formats that use this extension, 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

ACT files used with Photoshop can't be converted to any other format. The other file formats above can, you just probably can't use a file converter to do it. If the file can be converted, each specific program is likely capable of converting their own ACT file to a different 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, it's done through the File > Save As menu or some type of Export or Convert option.

Still Can't Open It?

At this point, the most likely reason for why the file won't open is that you're misreading the file extension. This is really easy to do since so many file extensions are spelled similarly. Unfortunately, a similar suffix doesn't necessarily mean similarities in format.

For example, ATC is the same three letters rearranged, but it's used for AutoCAD Tool Catalog files. It's used to customize the program workspace, so it's not related to the formats described on this page.

Several other examples could be given, like ACC and ATT. If you have one of those files, or something completely different, then you're not dealing with an ACT file and will need to research the file's actual extension.

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