ONIS 2.5 Free Edition

ONIS 2.5 Free Edition is a Windows DICOM viewer from DigitalCore, a Tokyo software company. It is aimed at students and non-professional users who need to open CT, MR, X-ray and other DICOM studies from a CD, a folder or a PACS. Most people searching for the ONIS DICOM viewer want this free package: a capable 2D viewer with multiplanar reconstruction (MPR) and MIP 3D, limited to a small local database.

The Free Edition is shareware (conditionally free): DigitalCore offers it as a limited entry-level edition of its commercial ONIS line. The local database holds only 15 patients, only one monitor is supported and extra plugins cannot be loaded. The paid ONIS 2.6 Professional and Ultimate editions remove these limits. DigitalCore’s current product, ONIS Viewer 3.0, is a separate paid program.

ONIS 2.5 Free Edition at a glance

What it does

• Reads DICOM files from any modality and manufacturer, including multi-frame images.
• Opens studies from a folder, a CD or DVD (DICOMDIR) or a DICOM server, and imports them into a local database.
• Connects to a PACS with the DICOM Client plugin (C-FIND, C-GET and C-MOVE as SCU; C-STORE as SCP and SCU).
• Single oblique MPR and Maximum Intensity Projection (MIP) volume rendering.
• Measurement and annotation tools: distance, angle, line, polyline, rectangle, polygon, oval, pen, arrow, text, ratio, orthogonal and parallel lines. Annotations can be exported to Excel.
• Series synchronisation, cine mode, custom window levels and per-modality display layouts.
• Exports images as DICOM, JPEG or BMP, and sends cropped snapshots to the Windows clipboard.
• Interface available in English, Japanese and French.

How dental teams use it

Import a CBCT or CT disc from an imaging centre

Insert the disc and open it through the optical source in ONIS. Browse the study list and import the study into the local database. Scroll through the axial slices, set a bone window level, and use the distance and angle tools to check dimensions on the slices. Remember the 15-patient limit: delete old studies from the local database when you no longer need them.

Look at a CBCT volume in other planes

Open the series and switch to the MPR view to see coronal, sagittal and oblique planes. You can check the bone around a tooth or the position of a structure in a plane that differs from the acquisition plane. Use MIP to get a quick overview of dense structures. ONIS has no panoramic curve, nerve tracing or implant library, so detailed implant planning still needs dedicated dental software.

Check images received from a PACS

If your clinic or partner radiology centre runs a PACS, add it as a DICOM node in the preferences (AE title, IP address and port), then query and retrieve studies. In the Free Edition, studies must be imported into the local database; opening them on demand from the server requires a paid edition.

Install and first run

• Windows: DigitalCore lists a dual-core CPU, 1 GB of RAM, a 1024×768 display and 30 MB of disk space as the minimum. Official compatibility stops at Windows 8 and Windows Server, so test it on Windows 10 or 11 before relying on it.
• macOS and Linux: not supported. DigitalCore’s iPad app, ONIS, is a separate client for images stored on ONIS Site Server and does not replace the Windows viewer.
• Gotchas: the 15-patient database fills up quickly. Anonymisation, calibration, colour lookup tables, DICOMDIR export and multiple monitors are disabled in the Free Edition.

Limitations

• Local database limited to 15 patients; single monitor only; no additional plugins.
• No anonymisation, image calibration, colour LUT or opacity tables in the Free Edition.
• No dental tools: no panoramic reconstruction, nerve canal marking or implant planning.
• Development of the 2.x line has stopped, and official system requirements do not list current Windows versions.
• DigitalCore markets ONIS Viewer 3.0 as FDA-cleared; it does not claim this for the 2.5 Free Edition.

ONIS vs alternatives

FAQ

Is the ONIS DICOM viewer Free Edition really free?

It is shareware (conditionally free). DigitalCore offers the Free Edition as a limited version (15 patients, one monitor, no extra plugins); the full feature set is in the paid Professional and Ultimate editions.

Where can I get an ONIS DICOM viewer download?

Use the official website, onis-viewer.com, for product information, documentation and the forum. DigitalCore also runs onis-app.com for its newer ONIS 3 products.

What is the difference between ONIS 2.5 Free Edition and ONIS 2.6?

ONIS 2.6 is the paid Professional and Ultimate line. It adds e-mail export, database filtering, multiple monitors, plugins and on-demand viewing from a server. The Free Edition stays on version 2.5.

Can ONIS read DICOM files from a dental CBCT?

Yes, if the CBCT software exports standard DICOM. You can scroll slices, view MPR planes and measure distances, but there are no dental-specific tools.

How can I view DICOM images on my computer?

Install a DICOM viewer such as ONIS on Windows, then open the CD or folder that contains the DICOM files (or the DICOMDIR file). Image viewers for JPEG files cannot read DICOM.

What is a DICOM viewer?

A DICOM viewer is a program that reads medical images in the DICOM format together with their patient and scan details. It lets you scroll through series, adjust contrast and measure.

Is there ONIS for Mac?

No. ONIS 2.5 Free Edition is Windows-only. On a Mac, use HorliX or another native macOS viewer.

Last checked against official sources: 26 September 2026 (developer website: onis-viewer.com). Versions and licence terms change — confirm on the developer's site before deploying in a clinic.