Source: https://openmyscan.com/en/guides/what-is-dicom-format Guide G–12 · Understanding # What is a DICOM file? DICOM is the language almost every hospital scanner speaks. A DICOM image file can store one image or multiple frames, together with metadata such as patient name, slice thickness, orientation, and more. You do not need to memorize the acronym to use your images; you only need to know they are not ordinary JPEGs. Gabriel Theis Founder, OpenMyScan 3 min read Updated October 26, 2026 Intermediate ## What is a DICOM file? A DICOM image file can contain one image or multiple frames plus metadata such as patient info, scanner settings, and image position. Other DICOM objects can hold different information. Photo apps can't open it because it's not a photo. Drop a DICOM folder into openmyscan.com to view the whole study in your browser. Open your scan free at openmyscan.com. 1. DICOM = Digital Imaging and Communications in Medicine, a shared standard, not a brand. 2. A DICOM image file may contain one image or multiple frames plus metadata; a complete study may need many files. Other DICOM objects can contain different information. 3. Open the whole folder in a DICOM-aware tool like OpenMyScan. Double-clicking one file in Photos will not work. ## Step 1 — What the letters mean Think of DICOM as a contract: manufacturers agreed on how to store medical images so any hospital system can exchange them. Your disc might say "DICOM" on the sleeve even when the filenames look like `IM0001` with no extension. ## Step 2 — What is inside one file Beyond the grayscale picture you eventually see, the file carries technical notes: how thick the slice is, which direction you are looking from, sometimes the MRI sequence name, and patient identifiers unless someone anonymized the study. That is why sharing "just one slice" can still leak private data. ## Step 3 — Why Preview, Photos, or Paint fail Consumer apps expect color photos. DICOM often uses 12–16-bit grayscale and needs a viewer that understands the header. OpenMyScan reads the folder locally and rebuilds the stack so you can scroll. ## Step 4 — Tools that actually open DICOM Hospitals use heavyweight clinical workstations. At home, our free [DICOM viewer](https://openmyscan.com/en/dicom-viewer) runs in a browser without installing anything; desktop alternatives exist but often look like cockpit dashboards. Pick the option you can actually navigate calmly. ## What confuses people first encountering DICOM? **I only see gibberish icons** You are probably in the wrong app. Drag the folder into OpenMyScan instead. **Which file do I open first?** None individually. Select the parent folder that holds them all. **Is DICOM the same as a radiology report PDF?** No. The PDF is words from the doctor; DICOM is the raw images. **Someone said DICOMDIR — what is that?** A table of contents file; keep it beside the slices so software can load the whole study. // open your scan Ready Open your scan right now OpenMyScan runs in your browser. Your files stay on your computer while you review them. [Open viewer](https://openmyscan.com/en/dicom-viewer) ## Common questions ### Is DICOM secure? The format is not encrypted by default. Protect USBs and cloud links the same way you would any medical document. ### What's the file size? One slice might be a few hundred kilobytes; entire studies often range from tens to hundreds of megabytes. ### Do all hospitals use DICOM? Modern imaging centers export DICOM routinely; if you received a CD, it almost certainly contains DICOM or a viewer pointing to it. ### Can I view my scan on my phone? No. The viewer needs a browser window at least 1200 pixels wide to show images alongside the series list. Use a laptop or desktop, or a tablet only if its browser window meets that width. Rotating an iPad to landscape does not guarantee enough space. Guides remain available on smaller screens. → try it now ## Open *your* scan Your original scan files are read on your device without a scan upload. Local previews and settings can persist after closing the tab; clear this site’s browser data to remove them completely. [Open viewer](https://openmyscan.com/en/dicom-viewer) [Browse all guides](https://openmyscan.com/en/guides) ## Keep reading [All 14 guides →](https://openmyscan.com/en/guides) [G–04 · Opening How to open .dcm files A .dcm file is a DICOM medical image. Here's how to open one file or a whole folder of them in your browser. Free, no install, no upload. Read guide](https://openmyscan.com/en/guides/how-to-open-dcm-files) [G–05 · Opening Best DICOM viewer for your scans: free and paid options Compare free and paid DICOM viewers for MRI and CT: OpenMyScan, MicroDicom, OsiriX MD and RadiAnt. Check accounts, local viewing, exports and license terms. Read guide](https://openmyscan.com/en/guides/best-free-dicom-viewer) [G–13 · Understanding MRI vs CT scan — difference explained for patients You were scheduled for 'a scan' and now you have two different names. Here's what MRI and CT actually are, and why both end up as DICOM on the CD. Read guide](https://openmyscan.com/en/guides/difference-between-mri-and-ct-scan) OpenMyScan is a viewer for images you already own. It is not a diagnostic tool, is not FDA- or CE-cleared, and does not replace professional medical advice. Always consult your doctor.