How to open .dcm files

A .dcm file is a single slice of an MRI or CT scan in DICOM format. Most people get them in a folder full of similar files (IM00001.dcm, IM00002.dcm, …) from a hospital CD or download. Normal image viewers — Photos, Preview, Paint — can't open them. OpenMyScan opens a folder of .dcm files in your browser, for free, without uploading anything.

Quick answer (3 steps)

1. Keep every .dcm (or extensionless) slice in one folder beside DICOMDIR if the hospital provided it.
2. Visit https://openmyscan.com in Chrome, Edge, Safari, or Firefox.
3. Drag the folder onto the drop zone — OpenMyScan assembles the stack locally; nothing uploads by default.

Step 1 — Treat the folder as the unit, not one icon

Double-clicking a lone .dcm in macOS Preview or Windows Photos fails because those apps expect vacation photos. Medical viewers read the whole directory so slice order, spacing, and orientation stay correct.

Step 2 — Copy before you open from slow media

If the files live on a CD or network drive, copy the folder to your Desktop first. Browsers read thousands of small files faster from an internal SSD, and some corporate laptops block optical drives entirely.

Step 3 — Scroll and sanity-check

After the progress bar finishes, use the slider or mouse wheel to move through slices. If a series list appears, click each entry — some studies bundle multiple directions (axial, sagittal, coronal). Brightness still needs a radiologist's eye; OpenMyScan is not diagnosing you.

Common problems on Mac and Windows

Someone emailed a single tiny .dcm

Politely ask for the full study — one slice lacks context.

Files have no .dcm suffix

That is normal; OpenMyScan reads the file header to detect DICOM instead of relying on filenames.

Drag-and-drop does nothing

Use the folder picker button or try another browser; some locked-down PCs block drag.

I see DICOMDIR but the screen stays blank

Ensure the slice files sit in the same folder — copy the whole directory tree the hospital gave you.

Open your scan right now

Browser-based. Free. Nothing uploads.

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Frequently asked questions