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1.      Why are there 2 downloadable versions of Horos? What’s the difference? Which one should I download?

Horos is continuously evolving. New features, enhancements, and bug fixes are always up and coming. The two versions available for download include the “Release Candidate” and the “Latest Version”. 


The Release Candidate includes the next step in Horos evolution. It has all the new fixes, advanced improvements, and milestones. However, the biggest difference between it and the Latest Version is that the Release Candidate is available to the community to provide feedback to us. Remember, Horos is an open source project and it would not be the success it is today without your valuable input. So, give the Release Candidate a try if you are open to providing us with constructive criticism about how we can overall improve Horos for the community. 


The Latest Version is a version that has officially been used and test driven by end users in the Horos community. 

2.           Does Horos run on Windows or Linux?

No. Horos currently only runs on a Mac computer with macOS 10.11 or later.

3.           What configuration of hardware is required to run on a Mac?

The short answer? -All Mac computers that can run macOS 10.11 or later. However, viewing medical images is memory intensive and can also require considerable CPU and GPU processing power. Our recommendation is to use Mac computers with i5 processors, 16GB RAM, and equipped with a discrete GPU or Intel Iris.

4.           What MacOS should I run for each version?

MacOS 10.11 or later.

5.           How do I stay updated on recent developments? 3

Horos features a notification system that will alert you when new updates are available.  4

6.           Can I store my images in iCloud?

We recommend that you don’t. It’s risky to store your images in iCloud. If you have more than one Mac computer logged into iCloud using the same Apple ID, and Horos is running on these computers, it’s probable that you will see your database getting corrupted. Even worse, your images could get overwritten by other images.

7.           How do I cite Horos in a paper? 3

Horos is a free and open source code software (FOSS) program that is distributed free of charge under the LGPL license at Horosproject.org and sponsored by Nimble Co LLC d/b/a Purview in Annapolis, MD USA. 4

8.           Is there any user training for Horos?

Yes! Horos Academy Entry Edition contains 4 modules: 1) First steps upon downloading Horos, 2) Image management, 3) 2D image visualization and manipulation, 4) 3D functionalities. While there are more editions to come, the Entry Edition is now available for purchase in English, Portuguese, and Spanish. If you want to learn how to maximize your use of Horos on your own pace, according to your schedule – this is it. However, if you find that you require more specific help, Horos offers paid support. Just fill out the form and one of our Horos experts will get in touch with you.  4

9.           What is the End User License Agreement for Horos? 3

As Horos is a free and open source code software (FOSS) program that is distributed free of charge under the LGPL license, your commitment to the terms of this license when installing Horos is a requirement. You can find the agreement when downloading Horos.  4

10.       Do I have to donate? 3

No, you are not required to make a donation to download or use Horos – it is completely free to download!  Horos, however, counts on the many generous contributions made by the community to continue operating and evolving. It is thanks to your donations that we have been able to hire additional programmers, add plugins, and continue to increase Horos’s functions. Purview has pledged to match every contribution made to at least double the value of your contribution.

Oh, and if you haven’t heard, Horos is now in pursuit of getting FDA and CE approvals! Don’t worry, Horos will remain a free, fully featured, open source product. However, this can only be possible with the help of users like you. The approval process is an expensive one, and Horos operates solely off of community support. You can help us reach our goal of $100,000 by making a donation today – every dollar counts! 

11.       What is a Study? 3

For purposes of calculation of fees, a Study is defined in the Digital Imaging and Communications in Medicine (DICOM) Standard section PS3.3-2011 and refers to a single patient during a single session on a single modality as identified by a single instance Unique Identifier (“UID”).