What is the MSD file format?
.msd files store maps generated by ArcGIS for use with ArcGIS Server's optimized map services. Each .msd is compiled from an .mxd document - the editable ArcMap map - and packages layer definitions, symbology, and table properties into a draw-optimized binary. Because .msd is a server-side compiled artifact, .msd files cannot be modified directly; to update the map you must edit the source .mxd and regenerate via ConvertToMSD or ArcMap's publish workflow.
.msd files are used by ArcGIS Server (versions 9.3-10.0) to render map images quickly over the web. The underlying GIS datasets are not embedded - they remain external; .msd carries only the rendering instructions.
.msd-based optimized map services were deprecated at ArcGIS 10.1 (2012). Esri replaced them with .sddraft and .sd service definitions, used in all current ArcGIS publishing workflows.
Security & safety
RISK: LOWAn MSD is a passive, compiled GIS server definition - it isn't an executable and contains no macros, so it can't run anything. It only references external datasets and is read by ArcGIS Server. The practical caveats are non-security: it's a proprietary, legacy artifact that only Esri software understands, and without the source .mxd it cannot be re-edited. Only deploy .msd files into a server from trusted internal sources, as with any published map content.
Format details
in a nutshellPrograms that open MSD files
Windows3 apps
ArcGIS Desktop (ArcMap)
Paid Use ArcMap's ConvertToMSD/MapToMSD tooling to generate or regenerate the .msd from a map document; ArcMap is the only app that authors MSDs. (ArcMap is retired - see ArcGIS Pro.)
ArcGIS Server (9.3-10.0)
Paid ArcGIS Server consumes the .msd to host an optimized map service. It reads the file; it isn't a desktop 'open' you do manually.
ArcGIS Pro
Paid The modern successor: open the source map in ArcGIS Pro and publish a web map/service (.sd), the current replacement for the legacy .msd workflow. Technical details
deep spec| Developer | Esri |
| Encoding | Proprietary binary (compiled map definition) |
| MIME type | application/octet-stream |
| Platform | Windows only |
| Typical file size | Tens of KB to a few MB (rendering definition only; GIS datasets are external) |
| Generated from | ArcMap document (`.mxd`) via `ConvertToMSD` or the ArcMap map publishing workflow |
| Consumed by | ArcGIS Server 9.3-10.0 optimized map services |
| Contents | Layer definitions, symbology rules, and table properties optimized for fast server-side rendering |
| GIS data storage | External only - underlying datasets are referenced, not embedded in the `.msd` |
| Editable | No - read-only compiled artifact; source `.mxd` must be edited and re-exported to update |
| Active lifespan | ArcGIS Server 9.3 (2008) through 10.0 (2010) |
| Deprecated | ArcGIS 10.1 (2012) - Esri discontinued optimized (MSD-based) map services |
| Superseded by | `.sddraft` / `.sd` service definitions (ArcGIS 10.1 and later) |
| File signature | None publicly documented - opaque proprietary binary with no known magic bytes |
| Released | 2008 (ArcGIS Server 9.3 - optimized map service publishing) |
| Latest version | ArcGIS 10.0; deprecated at ArcGIS 10.1 (2012) in favor of .sddraft/.sd service definitions |
| Specification | desktop.arcgis.com |
MSD conversions
Community Q&A
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