Frequently Asked Questions

Clique aqui para Português                 Haga clic aquí para Español

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?

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

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. Avoid these issues and try Horos Cloud Access, which enables you to easily query and download studies from the cloud directly to your Horos workstations.

7. How do I cite Horos in a paper?

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

8. Is there any user training for Horos?

Yes! We offer several options for training and help with Horos. 

The best way to learn how to use the viewer is the Horos Academy video tutorial. Taught by Horos experts, this video tutorial contains four modules covering the main functions in Horos:

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 at your own pace, according to your schedule - this is it. 

The Horos User Guide is a downloadable PDF document that contains almost 300 pages of detailed instructions for every menu and function in Horos. The extensive index provides a way to quickly and easily look up any topic for quick reference.

We also offer paid support. If you have a question or run into an issue, one of our experts will work with you personally to resolve it.

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

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.

10. Do I have to donate?

No, you are not required to make a donation to download or use Horos. It is totally free to download. Horos, however, counts on the many contributions made by the community. It is due 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! Donate to help us continue growing and making Horos better.