FAQs

Frequently Asked Questions

Table of Contents

What is Weasis?

Weasis is a standalone and web-based application designed for visualizing and analyzing images obtained from medical imaging equipment according to the DICOM standard. To learn more, visit the Weasis Medical Viewer page.

Which operating systems does Weasis run on?

Weasis runs on:

  • Windows — desktop installer or portable archive.
  • macOS — both Intel and Apple Silicon.
  • Linux — DEB, RPM, Flatpak, or Snap.

A web-launch option is also available — the Weasis Protocol opens the locally installed application from a portal click. See Download Weasis for the full installation matrix and platform notes.

Does Weasis require Java or any other framework?

No. The installers bundle everything Weasis needs, so there is no Java runtime to install or maintain. The only external requirement concerns 3D volume rendering, which needs a reasonably modern graphics card — see Download Weasis and the 3D viewer requirements.

Is there a portable version of Weasis?

Yes, on Windows: a portable archive is published next to the installer, so Weasis can be unpacked on a USB drive and run without installation or administrator rights — see Download Weasis.

Getting the viewer onto the media itself works one way only: the DICOM CD/DVD export can add that portable distribution to the ISO it writes, so the recipient starts Weasis straight from the disc. This is available only on Windows x86-64 — both to produce such an ISO and to run the embedded copy. On every other platform the export still writes a DICOM CD, just without a viewer on it; see Can Weasis be included in DICOM CDs or other removable media?

Does the web launch require Weasis to be installed?

Yes. The web launch is not a browser-only viewer — it uses the weasis:// URI scheme to hand launch parameters to the locally installed Weasis application. Each user must install Weasis once from the Download page; every subsequent click on a weasis://... link (typically generated by a PACS portal, EHR, or weasis-pacs-connector / ViewerHub) then reuses that local install. The previous in-browser Java Web Start distribution was discontinued in version 3.5 for security, configuration, and compatibility reasons.

Does Weasis need an internet connection?

No — Weasis runs fully offline once installed. It opens DICOM files from any local source (file system, USB drive, DICOM CD / DVD, ZIP archive) without network access.

Can Weasis open a DICOM CD or DVD?

Yes. Weasis reads the DICOMDIR of a DICOM CD, DVD or USB drive, and also opens a folder of DICOM files or a ZIP archive — by drag and drop, from the menu, or from the command line. Password-protected ZIP archives are supported on import. See Import DICOM Files, CDs and Archives.

Can Weasis open ordinary images such as JPEG or TIFF?

Yes. Besides DICOM, Weasis displays TIFF, BMP, GIF, JPEG, JPEG 2000, JPEG-XL, PNG, RAS, HDR and PNM files. If you need those images stored in a PACS rather than only viewed, convert them first with the Dicomizer.

Which DICOM object types can Weasis display?

Beyond ordinary and multi-frame images, Weasis displays Enhanced CT / MR / US volumes, MPEG-2 and MPEG-4, MIME-encapsulated documents such as PDF, Structured Reports, Presentation States and Key Object Selection, Segmentation, Radiotherapy objects, waveforms and ECG, audio and Parametric Maps. The full list is on the Features page.

Which DICOM transfer syntaxes and codecs are supported?

JPEG (baseline, extended and lossless), JPEG-LS, JPEG 2000, JPEG-XL, RLE and Deflated Explicit VR Little Endian, in addition to the uncompressed syntaxes. The DICOM Conformance Statement lists every transfer syntax and SOP class authoritatively; the Features page gives the summary.

Can Weasis query a PACS directly?

Yes. Weasis performs DICOM Query / Retrieve with C-FIND, C-GET and C-MOVE, and can also retrieve through WADO-URI. Nodes are configured in the import dialog — see Import DICOM Files, CDs and Archives.

Does Weasis support DICOMweb?

Yes — QIDO-RS to search, WADO-RS to retrieve and STOW-RS to store, over HTTPS and configurable per source. See DICOMweb Configuration, which also lists settings known to work with common providers.

Does Weasis compute SUV values for PET/CT?

Yes. When a PET or SPECT series is overlaid on a CT or MR base, Weasis reports SUV statistics over a region of interest. See PET/CT Image Fusion with SUV.

What does the 3D viewer require?

A graphics card supporting OpenGL 3.3 or later: the volume is ray-cast on the GPU with GLSL shaders, and nothing extra has to be installed. From OpenGL 4.3 a compute-shader backend is used instead, which renders at full resolution while you move the camera. The 3D viewer requirements section covers the capabilities involved and the settings that trade quality for fluidity.

Can Weasis convert photos, videos or PDF documents into DICOM?

Yes, with the Dicomizer: photos, scanned reports, videos and 3D models become DICOM objects that an archive can store alongside acquisitions from imaging modalities, with the patient, study and image tags set so they stay searchable. PDF documents are supported since v4.6.2.

Can Weasis print DICOM images?

Yes, to an ordinary printer or to a DICOM printer, with a choice of layout and print mode. See Print DICOM Images.

Is Weasis a certified medical device?

No. The open-source distribution of Weasis is not a certified medical device — it does not carry CE marking and is not FDA cleared. Any primary diagnostic use requires you (or your institution) to ensure full compliance with the laws and regulations applicable in your jurisdiction. The full disclaimer is displayed in a dialog the first time Weasis is launched and must be explicitly accepted before the application can be used; it is also reproduced on the Download Weasis page.

Being a medical device is a property of a product, not of a code base — and the same code can be both. At the University Hospital of Geneva, a variant called Weasis HUG is an in-house medical device: manufactured and used inside the institution under article 9 of the Swiss Medical Devices Ordinance (ODim), with a quality management system following ISO 13485:2016 and conformity to the general safety and performance requirements of Annex I of the European regulation 2017/745. It is deliberately not placed on the market and carries no CE marking — the in-house route covers use within the hospital that manufactures it, and nothing beyond that.

Does Weasis de-identify DICOM files?

No — and this matters. Weasis can hide patient identifiers on screen and in what it renders (screenshots, prints, image exports), which is useful for teaching and demonstrations, but that is not de-identification: text burned into the image pixels is not removed automatically, and DICOM files exported or sent from Weasis keep their original attributes. To de-identify DICOM data properly, use a tool built for it such as Karnak. Always review every image before sharing it.

Where can I ask questions about Weasis?

For general questions, use the Weasis forum or the GitHub discussions.

This website is organized by audience — start with the section that matches yours:

For the vocabulary itself — MPR, SEG, SR, SUV, DICOMweb — see the glossary.

How do I report a bug?

Open an issue on the Weasis GitHub issue tracker. To help the maintainers reproduce the problem, please include:

  • The Weasis version and your operating system.
  • A short description of what you did and what happened, with a screenshot if relevant.
  • The log files — set the log level to DEBUG or TRACE, restart Weasis, reproduce the issue, and attach boot.log and the most recent default.log* files. See How to configure and view log files for the full procedure.

How do I contribute a translation?

Weasis translations are managed on a community translation platform. To improve an existing language or add a new one, follow the Translating Weasis guide. End-user instructions for picking the active language are in the Language & Regional Settings tutorial.

Can Weasis be used for commercial purposes?

Yes — Weasis is available for commercial use, provided you comply with the terms outlined in the license.

How to cite Weasis in a publication?

Cite the software at the version you used — author Nicolas Roduit, title Weasis DICOM Viewer, the version, the URL https://weasis.org and the date you retrieved it. How to cite Weasis generates ready-made BibTeX, APA, Vancouver and plain-text entries for each release.

Why does Weasis use the Eclipse Public License?

The Eclipse Public License (EPL) is a commercially friendly open-source license approved by the Open Source Initiative (OSI). It offers several benefits:

  1. Business-friendly clauses — compared to LGPL, EPL includes more advantageous terms around patent retaliation and reverse engineering.
  2. Flexibility for derivative works — plugins and other extensions to Weasis can be distributed under any license (open source, freeware, or commercial). However, modifications to the existing source code of Weasis or its plugins must be made available to others if distributed.

Since version 3.7.0, the Weasis source code is distributed under a dual license: EPL-2.0 OR Apache-2.0. Users can choose the license that best fits their needs.

For more details, see the EPL 2.0 FAQ.

Can Weasis be included in DICOM CDs or other removable media?

Yes. Weasis can be embedded into a DICOM CD ISO so the recipient can launch it directly from the disc — currently supported on Windows x86-64 only. On other platforms, you can still produce a DICOM CD without the embedded viewer. See the CD/DVD Image section of the DICOM Export tutorial for the full procedure.

How do I enable Weasis logging?

To trace Weasis activities, enable the rolling log in the application preferences. See How to configure and view log files for the full configuration — including how to share the logs with the maintainers when filing a bug report.

Can I download DICOM files without a WADO server?

Yes — a WADO server is recommended, but not strictly required. Two alternative paths are supported:

  1. Build an XML manifest file — use the DirectDownloadFile and DirectDownloadThumbnail options described in the integration guide.

  2. Use the $dicom:get command — point at one or more files by URL:

    $dicom:get -r "http://external.server/images/MRIX_LUMBAR/img1.dcm http://external.server/images/img2.dcm"

    This works well for a small number of files. For larger studies or production deployments, prefer a proper WADO-RS / DICOMweb server — see DICOMweb Configuration.