To view it, your study is not uploaded anywhere
The file is read and drawn inside your browser. It doesn't travel to our servers. Neither do your measurements or your report: they live in this tab's memory and vanish when you close it, so they leave no trace even on a shared computer. The only thing that leaves is what you choose to send: if you request the link for your doctor, the study is encrypted on this very device before upload, the key travels inside the link and never reaches us, and the file is deleted when it expires. We do keep a tally of the visit itself — how many files you opened, how much they weighed, how long it took to render and whether anything failed — so we know the viewer is doing its job; never the file names, never anything inside them.
Not for primary diagnostic reading
A formal diagnosis is issued on radiology-calibrated monitors. This tool is for reviewing, measuring, comparing and walking your patient through the study — not a replacement for the reading station.
Free, no account
View any DICOM or NIfTI series, or the PDF that comes on the CD
Window and level, zoom, cine and series comparison
Measurements in real millimeters, angles and annotations
Multiplanar reconstruction (MPR) and 3D view
Write the report and export or print it
Download your own files as a zip
Needs an account
Save the study to a patient's record
File the signed report next to the visit note
Keep measurements and key images across sessions
Receive studies straight from your machines via worklist
Share the study with the patient without burning a CD
Quick answer
Why this used to be a problem on a Mac
Medical imaging arrives in the DICOM format, and macOS ships with nothing that opens it: Preview, which digests almost any image or PDF, does not support it. The viewer the lab burns onto the CD does not help either — it is a Windows executable, and on a Mac it simply does not run. And recent Macs no longer come with a disc drive at all.
For years the answer was to install a desktop viewer. It is still a valid option — the honest comparison is below — but for the most common case, which is looking at a study today, it is no longer necessary: the browser you already have open can read DICOM. If your problem starts with the physical disc, start with how to view a CT scan online, including what to do without a drive.
Opening it in Safari or Chrome, step by step
Copy the study to your Mac
From the CD (with an external USB drive), from the flash drive you were given, or from the lab’s portal. Copy the whole folder: a study is hundreds of files that belong together. A ZIP or RAR works as is, and so do loose JPG or PNG images.
Drag the folder onto the viewer above
Click “Open my study” or drag the entire folder onto the dotted area; there is also an “Open a folder” button. The viewer separates the series and sorts the slices by their real position, all on your own Mac.
Review with real tools
Window and level with tissue presets, length and angle measurements in real millimeters, cine, multiplanar reconstruction in all three planes and a 3D view. It accepts DICOM with or without an extension, ZIP, RAR and 7z archives, JPG/PNG images and NIfTI (.nii, .nii.gz), and opens the report PDF next to the images.
Export before closing the tab
Everything lives in the tab’s memory: close it and nothing remains. If you wrote a report or want to keep an image, export or print it before leaving.
Horos, OsiriX MD, Weasis and this viewer: an honest comparison
None of these programs is a bad option; they are tools with different friction and licensing. The right question is not “which is best” but how much installation and how much cost are justified for what you actually need to do:
| Viewer | License and cost | Installation | When it makes sense |
|---|---|---|---|
| This page | Free, no account | None: runs in Safari or Chrome | Viewing, measuring and sharing a study today, on any Mac, without installing anything |
| Horos | Free, open source (fork of OsiriX) | Desktop app; new releases have been rare for years | Someone who already knows it and reviews heavy studies daily on the same Mac |
| OsiriX MD | Paid | Desktop app for macOS | Radiologists who need a professional workstation on a Mac |
| Weasis | Free and open source (EPL license), commercial use included | Cross-platform desktop app | Anyone who wants an installed program at no cost, including in the practice |
The honest rule: if you review studies every day, offline, or with very heavy volumes, an installed desktop viewer still earns its place. For every other case — the patient’s CD, the study someone sent you, the second opinion, the look from another Mac — the installation is pure friction, and the browser removes it. The full guide to what a serious viewer must do is at free online DICOM viewer.
When the study has to stay on file
This viewer forgets everything when you close the tab — on purpose: that is what lets it be free and account-less. If you are a physician and the study belongs to your patient, what you need is for it to live in their record: the comparison against the prior study, the report next to the visit note, access from any computer. That same viewer is built into the Healthy Record electronic health record on every plan; the details are on the pricing page (in Spanish — the product serves clinics in Mexico).
Frequently asked questions
Is there a DICOM viewer for Mac that I don’t have to install?
Yes: this very page. The viewer runs inside Safari or Chrome on macOS, it is free and asks for no account. Drag in the study folder, the ZIP (or RAR) from the CD, loose JPG/PNG images or a NIfTI file and read it with window/level, measurements in real millimeters, multiplanar reconstruction and a 3D view. To view it, the study is read inside your browser and is not uploaded to any server.
Does it work on Apple Silicon Macs (M1, M2, M3, M4…)?
Yes, and on Intel Macs too. Because the viewer runs inside the browser it does not depend on the processor architecture: there are no binaries to translate and no separate builds. That is a practical advantage over older desktop viewers, which were compiled for Intel and rely on compatibility layers on an Apple Silicon Mac.
Is Horos still a good option for Mac?
Horos is free and open source — it started as a fork of OsiriX — and it remains a capable desktop viewer. Its weak spot is friction: you have to download and install it, and new releases have been rare for years, which shows on recent systems and hardware. If you review heavy studies every day on the same Mac and already know it well, keeping it makes sense; if what you want is to look at a study today, the browser saves you the whole installation.
What is the difference between this viewer and OsiriX MD?
They are tools for different jobs. OsiriX MD is a paid, very complete desktop viewer built as a professional radiology workstation for macOS. The viewer on this page is free, runs in the browser and is meant for reviewing, measuring, comparing and sharing a study without installing anything — not for signing the diagnosis, which is done on calibrated displays. If reading studies is your daily job, a dedicated workstation is justified; for everything else, the browser gets it done.
How do I open the CD of my scan on a Mac without a disc drive?
Copy the whole folder off the disc with an external USB drive, or ask the imaging center for the study as a download or a ZIP; many portals also hand out the images as JPG. Whatever you end up with — the folder, the ZIP, the RAR, or the JPGs — drop it on the viewer above and it opens in the browser.