Recently while editing some images in Adobe Camera RAW (ACR), I noticed an additional, new, “.acr” sidecar file. In the past, I’ve written about the .XMP files that are created by Adobe Photoshop Lightroom Classic and Adobe Camera RAW when you edit raw images. This .ACR file was created in addition to the .XMP file, and that made me curious. So what are “.ACR files”? And can you delete them if you don’t like them? In this article, I’m sharing what I’ve learned about the .acr file format through experimentation, trial, and error…
What We Know About the .ACR File Format
A little research and experimentation brought up the following details about .ACR files:
- .ACR files are created by Adobe Camera RAW (often abbreviated to ACR) when certain features are used. This could be a part of the new AI powered masking tools (subject selection or Sky Selection), or “Lens Blur” features.
- When you open a RAW file from your camera in Photoshop or Bridge, Adobe Camera RAW (ACR) opens up, so that you can process the RAW file. If you’re not using a .dng file, ACR writes the settings that you use in your processing into .xmp files (which are quite useful) – I’ve written about earlier xmp files earlier – and in the last few versions of ACR, it also writes files with the .acr extension when needed.
- Unlike .XMP files, which are readable text files, .ACR files are binary. This means that we can’t see the data that they hold.
- .ACR files seem to hold information like filter presets, and Depth Mask information for each photograph, ie: data that can’t be stored in a .xmp file as text settings. This comes into use when masking facial features, using “lens blur” etc.
- It is an additional file, that is created with the same file name as your RAW file, in addition to .xmp files. When you rename your RAW file in Adobe Bridge, the .xmp and .acr files also get renamed.
- If you don’t copy .acr files, to a new folder, then the depth map information will have to be regenerated to use lens blur, and this could take additional time, especially if you are doing it for many photographs at the same time. That said, you don’t have to copy the .acr files if you don’t want to.
- Adobe has not shared much technical information about .acr files created by Adobe Camera RAW (ACR), so we have to guess, and speculate based on software behaviour. If, and when Adobe decides to release any technical documentation, I’ll update this page so that you’re made aware of the development.
- .acr files don’t seem to be created when using a .dng file, or if you’re using the same features in Adobe Photoshop Lightroom Classic (LrC). It’s limited to Adobe Camera RAW for now. Lightroom Classic seems to store this data in the Lightroom Catalog file. I’m not 100% sure about this, so I’m open to new information about Lightroom Classic and .acr files.
Should You Keep The .ACR file?
If you’re editing RAW files, and you’re using ACR’s masking tools, or Lens Blur, then it makes sense to keep the files if you’re not short of disk space, and would prefer to work fast. When using lens blur, the adding depth map information for a 21 Mpx image, added about 1.5MB in file size to the associated .acr file…
Next, let’s explore what happens if we delete the file.
What Happens if You Delete .acr files?
When I deleted the .acr file and then re-opened my .cr2 raw file, I saw no difference. The lens blur, and all my edits were intact. I’m on a reasonably fast computer, so I didn’t notice any speed differences when opening the file. When I checked my edits and closed ACR by pressing the ‘done’ button, the file was recreated…
So, in short, you can safely delete, or not copy .acr files if you choose to do so. Camera Raw will recreate the files if it needs to.
If you’re short on space, delete the files.
More Information
.acr files seem to have come on the scene with Adobe Camera Raw 14.0 and later, when the AI masking tools were introduced.
If you, or anyone you know has more information about .acr files and how they’re used by Adobe Camera Raw, please leave a comment, or connect with me via email. I’d love to learn more about these files.
Does the ACR file carry details on any AI used? If it does, will it be a telltale file to Microstock sites like iStock by Getty images?
I don’t think that this is a cause for concern, as only the .jpg files that you upload would be able to pass on information to microstock sites … and they do do that…
I believe that at the moment, Adobe adds a metadata tag to JPG files that have been created from .PSDs that have AI layers still active (the metadata is removed if you flatten the image, is my current understanding). I’ll have to look into this in more detail, and document my findings in another article. Thanks for bringing up the topic.