FILE FORMAT GUIDE
DCM File (.DCM): What It Is & How to Open It
A DCM file commonly stores one DICOM SOP instance with file meta information and a data set. The content may include images, reports or other medical objects.
Quick facts
- Extension
- .dcm
- Format
- DICOM File
- Category
- document
- MIME type
- application/dicom
- Standard / developer
- DICOM Standards Committee / NEMA
- Open with
- Weasis
What is DCM?
A Part 10 DICOM file starts with a 128-byte preamble followed by DICM at offset 128 and file meta elements. DICOM data sets without that file-format wrapper also exist, so force-parsing arbitrary input is unsafe evidence.
How to open DCM
WeasisWindows / macOS / Linux
Open the DICOM file or containing folder in Weasis. Medical images can include sensitive health information, so use an approved device and workflow.
Common uses and compatibility
- Exchange a DICOM SOP instance with transfer-syntax metadata
Things to check
- DICOM data can contain sensitive patient information; reading metadata does not make a file de-identified or clinically validated.
Advanced inspection
These developer and command-line workflows inspect structure or metadata. They are not the default way most people open the file.
pydicomCommand-line tool or library
Use pydicom.dcmread("image.dcm", stop_before_pixels=True) for an initial metadata read. Do not use force=True on unknown input: the documentation shows it can defer errors for non-DICOM data.
Technical details
- Signature
- 44 49 43 4D (DICM at offset 128)
- Encoding
- Not applicable
- Container
- DICOM PS3.10 file meta information plus one data set
- Compression
- Not reviewed
Related formats
- JPEG Image
JPEG may be used for a rendered image export, but it does not preserve the full DICOM dataset and clinical context.
- Portable Network Graphics
PNG may carry a rendered raster image, but it is not a replacement for the metadata and structure of a DICOM file.
Sources & review
Sources reviewed 2026-09-19.