Petrsvihlik WopiHost Save

ASP.NET Core MVC implementation of the WOPI protocol. Enables integration with WOPI clients such as Office Online Server.

Project README

Logo WopiHost

Build & Test codecov Maintainability CodeFactor FOSSA Status .NET Core

Package Version Downloads
WopiHost.Abstractions NuGet NuGet
WopiHost.Core NuGet NuGet
WopiHost.Discovery NuGet NuGet
WopiHost.FileSystemProvider NuGet NuGet
WopiHost.Url NuGet NuGet


This project is a sample implementation of a WOPI host. Basically, it allows developers to integrate custom datasources with Office Online Server (formerly Office Web Apps) or any other WOPI client by implementing a bunch of interfaces.

Features / improvements compared to existing samples on the web

  • clean WebAPI built with ASP.NET Core MVC (no references to System.Web)
  • uses new ASP.NET Core features (configuration, etc.)
  • can be self-hosted or run under IIS
  • file manipulation is extracted to own layer of abstraction (there is no dependency on System.IO)
    • example implementation included (provider for Windows file system)
    • file identifiers can be anything (doesn't have to correspond with the file's name in the file system)
  • custom token authentication middleware
  • DI used everywhere
  • URL generator
    • based on a WOPI discovery module
  • all references are NuGets



Building the app

The WopiHost app targets net7.0 exclusively.

If you need a version that's targeting an older version of .NET, check out the releases:

If you get errors saying that Microsoft.CobaltCore.*.nupkg can't be found, then just remove the reference or see the chapter Cobalt below.




Parameter Sample value Description
Wopi:StorageProviderAssemblyName "WopiHost.FileSystemProvider" Name of assembly containing implementation of WopiHost.Abstractions interfaces
Wopi:StorageProvider:RootPath ".\\wopi-docs" Provider-specific setting used by WopiHost.FileSystemProvider (which is an implementation of IWopiStorageProvider working with System.IO)
Wopi:UseCobalt true Whether or not to use MS-FSSHTTP for file synchronization. More details at Cobalt



Parameter Sample value Description
Wopi:HostUrl "http://wopihost:5000" URL pointing to a WopiHost instance (above). It's used by the URL generator.
Wopi:ClientUrl "http://owaserver" Base URL of your WOPI client - typically, Office Online Server - used by the discovery module to load WOPI client URL templates
Wopi:StorageProvider:RootPath "..\\..\\WopiHost\\wwwroot\\wopi-docs" Provider-specific setting used by WopiHost.FileSystemProvider (which is an implementation of IWopiStorageProvider working with System.IO)
Wopi:Discovery:NetZone "InternalHttp" Determines the target zone configuration of your OOS Deployment. Values correspond with the NetZoneEnum.

Additionally, you can use the secret storage to configure both of the apps.

Running the application

Once you've successfully built the app you can:

  • run it directly from the Visual Studio using IIS Express or self-hosted.
    • make sure you run both WopiHost and WopiHost.Web. You can set them both as startup projects
  • run it from the cmd
    • navigate to the WopiHost folder and run dotnet run
  • run it in IIS (tested in IIS 8.5)
    • TODO

Compatible WOPI Clients

Running the application only makes sense with a WOPI client as its counterpart. WopiHost is compatible with the following clients:

Note that WopiHost will always be compatible only with the latest version of OOS because Microsoft also supports only the latest version.

The deployment of OOS/OWA requires the server to be part of a domain. If your server is not part of any domain (e.g. you're running it in a VM sandbox) it can be overcome by promoting your machine to a Domain Controller. To test your OWA server follow the instructions here. To remove the OWA instance use Remove-OfficeWebAppsMachine.


In the past (in Office Web Apps 2013), some HTTP actions required support of MS-FSSHTTP protocol (also known as "cobalt"). This is no longer true with Office Online Server 2016. However, if the WOPI client discovers (via SupportsCobalt property) that the WOPI host supports cobalt, it'll take advantage of it as it's more efficient.

If you need or want your project to use Cobalt, you'll need to create a NuGet package called Microsoft.CobaltCore.nupkg containing Microsoft.CobaltCore.dll. This DLL is part of Office Web Apps 2013 / Office Online Server 2016 and its license doesn't allow public distribution and therefore it's not part of this repository. Please always make sure your OWA/OOS server and user connecting to it have valid licenses before you start using it.

Using in your web project




Known issues / TODOs

There is plenty of space for improvements in the overall architecture, implementation of the [MS-*] protocols or just finishing the TODOs in the code. Lot of refactoring still needs to be done and also the code style has to be unified. So please feel free to help me out with it :)



Useful resources

Building WOPI Host


Building WOPI Client

FOSSA Status

Open Source Agenda is not affiliated with "Petrsvihlik WopiHost" Project. README Source: petrsvihlik/WopiHost

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