Free online CT scan viewer: read your CT in the browser

1

Get the files off the disc or drive

Copy the whole folder from the CD or USB drive to your computer. The images usually live inside a folder named DICOM or IMAGES, and the files are often called IM000001 or similar with no extension at all — they are still DICOM. If the imaging center gave you a .zip, use it as it is.

2

Open them in the viewer on this page

Click “Open my CT scan” and select all the files, or drag the entire folder onto the dotted area. On a computer there is also an “Open a folder” button that loads the whole study in one go; on iPhone and iPad the system never offers a folder picker, so select the files in bulk or pick the .zip instead.

3

Let your browser build the volume

The viewer separates the series, sorts the slices by their real position in your body and reconstructs the volume on your own machine. A progress screen counts the files as they load. Nothing is uploaded: open your browser’s Network tab and you won’t see your scan leave.

4

Pick a window preset

Choose the tissue you care about — lung, mediastinum, bone, brain, abdomen — and the slice transforms. Without this step a CT looks like a flat gray smudge; the exact numbers behind every preset are in the table further down.

5

Scroll, measure, reconstruct

Move through the slices with the mouse wheel, the arrow keys or the cine control. Trace lengths and angles — they come out in real millimeters because the study carries its physical calibration. Open MPR to navigate all three planes and the 3D view to make sense of a finding.

6

Export before you close the tab

Everything lives in the memory of this tab and vanishes when you close it. If you wrote a report or captured key images, export or print them first.

A CT scanner doesn’t take a photograph — it measures a volume. The machine rotates an X-ray tube around you and computes cross-sectional slices, typically a few hundred of them, each one a map of tissue density a fraction of a millimeter to a few millimeters thick. What lands on your CD is that stack of slices, and usually more than one series: the same volume may be reconstructed twice, once with a soft-tissue kernel and once with a sharper bone kernel, and studies with intravenous contrast add phases acquired at different times.

The files inside the folder are not in any useful order — their names reflect the order of writing, not of anatomy. A proper CT viewer groups them by series and sorts each series by the recorded table position, which is the only ordering that lets the volume be rebuilt without distortion. That is also why you should always open the whole folder: a single slice out of context is nearly meaningless, and a partial series can’t be reconstructed. If your study came as a .zip or a NIfTI volume, the general DICOM viewer guide covers how each format opens here.

CT pixels are physical measurements. Each one carries a density value in Hounsfield units (HU), on a scale where air sits near −1000, water at 0 and dense cortical bone above +1000. That’s thousands of possible values — and a screen can only display about 256 shades of gray. The window (width) decides how wide a band of densities gets spread across those grays, and the level (center) decides where the band sits. Everything outside the band is crushed to plain black or white.

These are the presets built into the viewer on this page, with their actual values:

Presets are starting points, not laws: you can drag to fine-tune the window at any moment, and the viewer initially applies whatever setting the technologist stored in the study itself. The habit worth copying from radiologists is to review the same anatomy under more than one window — a lung nodule and a rib fracture live in the same slices but in different bands of density.

CT slices are acquired axially — as if the body were cut across, slice by slice. But once the volume is rebuilt, nothing forces you to stay in that plane. Multiplanar reconstruction (MPR) re-cuts the same volume coronally (front to back) and sagittally (side to side), and the three views stay synchronized: click a point in one plane and the other two jump to it. Long structures — the spine, the aorta, a femur — often only make sense outside the axial plane.

The 3D volume view renders the whole dataset at once. It adds little for a subtle soft-tissue finding, but it is unbeatable for understanding shape — the course of a fracture, the branching of vessels — and it is the view that finally makes a study legible to the person it belongs to. Both tools run in your browser, on your own graphics card.

The honest limit: this is a review viewer. Formal diagnosis happens on calibrated radiology displays — use this page to look, measure, compare and understand, and keep the radiologist’s report as the reference.

To view it — nothing leaves your computer. The browser reads the files you selected, decodes every slice and assembles the volume on your own machine. There is no upload, we keep no copy, and when you close the tab nothing remains. You can verify this yourself in the browser’s Network tab: while you scroll your scan, no request carries your images out. That is also why no account is needed.

There is exactly one exception, and it only happens if you ask for it: the button that sends the study to your doctor. In that case the study is uploaded, but encrypted on your device before it leaves. The decryption key travels inside the link, in the part after the “#” — the one part of a URL a browser never sends to any server — so we store bytes we cannot read. The link expires after 72 hours, works a limited number of times, and can be revoked; afterwards the file is deleted. The flip side: lose the link and the study is unrecoverable.

The free viewer forgets everything when the tab closes — fine for looking at your own scan, not fine for a clinic. When the CT belongs to your patient, you’ll want it next to the previous one, the report filed with that visit’s note, and access from any of your consultation rooms. That takes a records system behind the viewer: the same engine on this page ships inside Healthy Record’s clinical records, where uploaded studies stay in the patient’s history with access control and an audit trail. There is a 14-day trial if you want to see it with your own studies.