What is the WSP file format?
.wsp is a SharePoint Solution Package - a deployment file used to install custom features, assemblies, and templates into Microsoft SharePoint on-premises environments. Despite the .wsp extension, the file is a standard Microsoft Cabinet (.cab) archive, identifiable by the MSCF magic bytes (4D 53 43 46) at offset 0. Renaming a .wsp to .cab allows it to be inspected in Windows Explorer or with 7-Zip.
Inside the archive, a manifest.xml file acts as the root descriptor, declaring the solution identity, features, .NET assemblies (DLLs), ASPX/ASCX page templates, JavaScript, CSS, and image resources. Deployment is performed via PowerShell (Add-SPSolution then Install-SPSolution) or SharePoint Central Administration - not by opening the file directly.
Two solution types exist: farm solutions run with full trust and have unrestricted server access; sandbox solutions operated in a restricted process and are deprecated since SharePoint 2013 and unsupported in SharePoint Online. For SharePoint Online and Microsoft 365, the modern successor is the .sppkg SharePoint Framework package format.
Visual Studio generates .wsp files automatically when building SharePoint projects. The solution schema version declared in manifest.xml targets SharePoint 2007 through SharePoint Subscription Edition. .NET assemblies within the package carry Strong Name signatures for integrity verification.
Security & safety
RISK: MEDIUMA WSP (farm solution) is a full-trust package that deploys compiled .NET assemblies to a SharePoint server. A malicious .wsp could contain code that runs as the application pool identity (often a domain service account). Never deploy a WSP from an untrusted source without reviewing the manifest.xml and DLL contents (use 7-Zip to inspect first, then check assemblies with a decompiler like ILSpy). Sandbox solutions are lower risk due to the sandboxed process, but are deprecated. SharePoint Online does not accept WSP files - only vetted .sppkg via the app catalog.
Format details
in a nutshell- Microsoft Visual C++ Workspace Info File - Very old Visual C++ versions (pre-2000s) used .wsp for workspace state files; effectively obsolete and rarely encountered.
- WordPerfect Macro/Workspace file - Older WordPerfect versions used .wsp for workspace or macro storage; legacy only.
Programs that open WSP files
Windows4 apps
7-Zip
Open-source Right-click the .wsp > Open archive (or rename to .cab first). Inspect the manifest.xml, DLLs and feature files without deploying. 
Microsoft Visual Studio
Paid Open or create a SharePoint Solution project; the Package Designer shows the WSP contents and allows modifications before re-packaging. 
SharePoint (PowerShell)
Built-in Add-SPSolution -LiteralPath solution.wsp; Install-SPSolution -Identity solution.wsp -WebApplication http://sitename. Run in SharePoint Management Shell on the server.
SharePoint Central Administration
Built-in System Settings > Farm Solutions > Upload Solution - deploy the .wsp via the web UI (no PowerShell required). Technical details
deep spec| Container format | Microsoft Cabinet (CAB) - magic bytes 4D 53 43 46 (MSCF) at offset 0 |
| Byte order | Little-endian (CAB format standard) |
| Compression | MS-ZIP (DEFLATE-based) or LZX per-file entry within the CAB |
| Root descriptor | manifest.xml - XML file declaring solution ID, features, .NET assembly paths, and file mappings |
| Assembly integrity | .NET DLLs carry Strong Name signing (public key token) for integrity verification |
| Solution types | Farm solution (full trust, full server access) vs. sandbox solution (restricted process, deprecated in SharePoint 2019 and unsupported in SharePoint Online) |
| Deployment commands | Add-SPSolution (registers to farm) then Install-SPSolution (activates deployment), via SharePoint Management Shell |
| Solution schema version | Declared in manifest.xml; targets SharePoint 2007, 2010, 2013, 2016, 2019, or Subscription Edition |
| Typical contents | manifest.xml, .NET DLLs, Feature XML definition files, ASPX/ASCX templates, JS/CSS/image resources |
| Typical file size | 10 KB - 500 MB (small feature to large enterprise farm solution) |
| Development tool | Microsoft Visual Studio SharePoint project type generates .wsp files via its Package system |
| Modern successor | .sppkg (SharePoint Framework package) for SharePoint Online and Microsoft 365 |
| MIME type | application/octet-stream (no registered MIME type; CAB content sometimes identified as application/x-cab) |
| Released | Windows SharePoint Services 3.0 / SharePoint 2007 |
| Latest version | SharePoint Server Subscription Edition (2024) / SharePoint Online |
| Specification | learn.microsoft.com |
WSP conversions
Community Q&A
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