Software & Apps File Types What Is an ACO File? How to open, edit, & convert ACO files By Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated November 18, 2019 Lifewire / Tim Fisher File Types Design Cryptocurrency MS Office Windows Linux Google Drive Apps File Types Backup & Utilities View More Tweet Share Email A file with the ACO file extension is an Adobe Color file, created in Adobe Photoshop, that stores a collection of colors. The name of each color is also saved in this file. You can see the names by hovering the mouse cursor over the color in the Swatches window in Photoshop. Some ACO files may instead be ArCon Project files used with the ArCon architectural software, but we have very little information on them. How to Open an ACO File ACO files that are Adobe Color files can be opened with Adobe Photoshop in a couple different ways. The easiest way to open an ACO file is to use the Edit > Presets > Preset Manager... menu item. Change the "Preset Type:" to Swatches and then choose Load... to browse for the ACO file. Another method is to access the Window > Swatches menu. On the top right of the small window that opens in Photoshop (probably to the right of the program) is a button. Click that button and then choose the Load Swatches... option. No matter which method you use, when browsing for the ACO file you want to open, make sure the "Files of type:" option is set to ACO and not ACT, ASE, or anything else. While you can make your own custom swatches in Photoshop (through the Save Swatches... option using the second method above), the program does include a handful of them when it's first installed. These are located in the \Presets\Color Swatches\ folder of the installation directory and are automatically loaded in Photoshop when it's opened. ArCon Project files are associated with software called ArCon (planTEK). If you find that an application on your PC does try to open the ACO file but it's the wrong application or if you would rather have another installed program open ACO files, you can change the default program for a specific file extension in Windows. How to Convert an ACO File The ACO format is a special format used only in Photoshop, so there's no reason to convert an ACO file to any other format. In fact, Photoshop can't even see/browse/open the file if it's saved under a different file extension, so converting it would be useless. Although ACO files are an exception, in this case, it's normally true that you can use a free file converter to convert one file format to another like you can with popular formats like DOCX and MP4. If you manage to get an ACO file to open with ArCon, then you might be able to use it to convert the ACO file, too. However, project files like these are normally saved in a proprietary format that's only useful within the program that created them. Plus, given that it's a project file, it likely holds other things pertinent to the project like images, textures, etc., so it's unlikely that it can be converted to some other format. Still Can't Open Your File? If your file doesn't open correctly with the programs we linked to above, double-check the file extension to confirm that it really does read ".ACO" and not something that just looks similar. Some files share similar looking suffixes even though they are not related and cannot be opened in the same way. For example, another Adobe file format that has a file extension that shares a couple of the same letters as .ACO, is ACF. AC files are another example. They use a file extension that's just one letter off of an ACO file but are actually unrelated to Adobe Photoshop and ArCon. Instead, AC files could be Autoconf Script files or AC3D 3D files.