What is the VSS file format?
A .vss file is a Microsoft Visio stencil - a library of reusable shapes called "masters" that users drag and drop into Visio diagrams. Unlike a drawing file, a .vss stencil contains no diagram content of its own; it is purely a shape library.
The format uses the OLE2 Compound File Binary (CFBF) container, the same binary wrapper as legacy .doc and .xls files. It is recognizable by the D0 CF 11 E0 magic bytes at offset 0, though those bytes identify only the OLE2 container, not Visio specifically. The actual shape data lives inside internal OLE streams: VisioDocument (geometry, connection points, text, and styling for each master) and VisioInformation (stencil metadata).
The binary .vss format was the standard stencil format from Visio 1.0 (1992) through Visio 2010. Microsoft replaced it with .vssx in Visio 2013, which uses the ZIP-based Open Packaging Conventions format. Visio 2013 and later can still open .vss files but no longer create them.
Stencil packs from hardware and software vendors - Cisco, AWS, network equipment manufacturers - are still widely distributed as .vss files for compatibility with older Visio installations. LibreOffice Draw can partially open .vss files via its libvisio library, though full stencil support is limited. draw.io does not import .vss directly.
Security & safety
RISK: LOWA plain VSS stencil contains shape geometry and metadata - no macros and low risk. The macro-enabled stencil variant is VSSM, which can carry VBA - treat VSSM from untrusted sources with caution. Opening VSS in LibreOffice Draw, which doesn't run Visio VBA, is a safe way to inspect a stencil you're unsure about. Many vendor stencil packs are distributed as .vss - obtain them only from the official vendor websites (e.g., cisco.com, microsoft.com).
Format details
in a nutshell- Microsoft Volume Shadow Copy Service snapshot file - Windows uses .vss internally for shadow copy snapshot metadata; completely unrelated to Visio and not user-facing.
Programs that open VSS files
Windows3 apps
Microsoft Visio
Paid In Visio, use Shapes pane > More Shapes > Open Stencil and select the .vss file. The shapes appear in the stencil panel for drag-and-drop use in drawings. 
LibreOffice Draw
Open-source LibreOffice Draw uses the libvisio library and can partially render VSS stencil contents. Fidelity is limited - use Visio or the Viewer for full stencil use. 
Microsoft Visio Viewer
Free Free legacy standalone viewer for Visio files; can open VSS stencils to view their shapes. 
macOS2 apps
OmniGraffle
Paid OmniGraffle can import Visio stencils (.vss) - open the file to add the shapes to OmniGraffle's library. Good for Mac users who work with Visio stencils.
LibreOffice Draw
Open-source Open the .vss to view its shape contents on macOS (Visio has no macOS version). Fidelity is partial. 
Linux1 app
LibreOffice Draw
Open-source Open the .vss via libvisio; partial rendering of shapes. The only practical Linux option. Technical details
deep spec| Container | Microsoft OLE2 Compound File Binary (CFBF) |
| Magic bytes (offset 0) | D0 CF 11 E0 A1 B1 1A E1 (OLE2 compound document signature) |
| Byte order | Little-endian |
| Internal OLE streams | VisioDocument (master shapes), VisioInformation (metadata), SummaryInformation, DocumentSummaryInformation |
| Shape master content | Geometry paths, connection points, text labels, shape data fields, formatting properties |
| MIME type | application/vnd.visio |
| Typical file size | 50 KB - 10 MB (small custom stencil to large vendor pack with hundreds of shapes) |
| Read/write compatibility | Visio 4.x through Visio 2010 |
| Read-only (newer Visio) | Visio 2013, 2016, 2019, 365 can open VSS files but cannot save in this format |
| Successor format | VSSX - ZIP/OPC-based stencil introduced in Visio 2013 |
| Published specification | [MS-VSS] via Microsoft Open Specifications Program |
| Integrity mechanism | OLE2 FAT sector chaining; no per-shape CRC of stencil content |
| Third-party read support | LibreOffice Draw (partial, via libvisio); draw.io does not import VSS |
| Typical stencil contents | Shape libraries: network (Cisco, Juniper), AWS architecture, flowchart, org chart symbols |
| Released | 1992 (Visio 1.0 era); VSS binary stencil format through Visio 2010 |
| Latest version | Visio 2010 (binary format); replaced by VSSX in Visio 2013 |
| Specification | learn.microsoft.com |
VSS conversions
Community Q&A
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