What is the OPJ file format?
.opj files are the native project format of OriginLab Origin and OriginPro, a scientific graphing and data-analysis application widely used in research and engineering.
Files with the .opj extension bundle all project content into a single proprietary binary file - worksheets and workbooks, 2D and 3D graphs, matrices, analysis results, notes, and embedded LabTalk or Origin C scripts. Because everything is stored together, opening an .opj file restores the entire session exactly as it was saved, including layouts and analysis pipelines.
The format is an undocumented proprietary binary container; the community-maintained liborigin library has partially reverse-engineered it to allow data extraction by third-party tools. Older versions of Origin cannot always open projects saved by much newer versions, so teams sharing files should verify version compatibility.
Origin 2018 introduced the .opju format (Unicode Origin Project), which supersedes .opj for new work. Legacy .opj files remain readable in current Origin versions. The free Origin Viewer opens both .opj and .opju files without a full Origin license.
Do not confuse this format with the OrCAD Capture .opj project file, which is a plain-text circuit-design descriptor - a completely unrelated format that shares the same extension.
Security & safety
RISK: LOWOPJ is a data/graphing project, not an executable. Embedded LabTalk/Origin C scripts run only inside Origin, so only open projects from sources you trust. The file is not encrypted; treat unpublished research data accordingly.
Format details
in a nutshell- OrCAD Capture Project - Cadence OrCAD Capture project file (plain text) that references a .dsn design plus settings; about 15% of .opj files.
- OpenJUMP Project - Project/workspace file for the OpenJUMP open-source GIS application.
Programs that open OPJ files
Windows3 apps
Origin / OriginPro
Paid File → Open and select the .opj (or drag it onto Origin). Native editor for full editing.
Origin Viewer
Free Install the free Origin Viewer, open the .opj, browse sheets/graphs and copy data out (view-only). 
macOS1 app
Linux1 app
Technical details
deep spec| File type | Proprietary binary project workspace |
| Developer | OriginLab Corporation |
| Encoding | Binary |
| Byte order | Little-endian |
| Container | Proprietary OriginLab project container |
| Compression | Internal (non-standard, not publicly documented) |
| Encryption | None (read-only flag possible, but no encryption) |
| Typical file size | 100 KB - 500 MB |
| Magic bytes | No stable public signature; identified by extension and content |
| Project contents | Worksheets, workbooks, 2D/3D graphs, matrices, analysis results, notes, and embedded LabTalk/Origin C scripts |
| Format versioning | Tracks the Origin release that wrote it; older Origin may not open projects from much newer versions |
| Successor format | .opju (Unicode Origin Project), introduced in Origin 2018 |
| Free viewer | Origin Viewer opens .opj and .opju without a paid license |
| Associated OS | Windows |
| Reverse-engineering | Community liborigin library partially reverse-engineered the structure for third-party data extraction |
| Released | Early 1990s (Origin, the technical graphing/analysis suite) |
| Latest version | OPJ (legacy non-Unicode); superseded by OPJU Unicode format in Origin 2018 |
| Specification | www.originlab.com |
OPJ conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about OPJ files.
