title: How to create Office COM Add-in, which is deployable without admin rights
body: <p>I am looking for an approach to develop a MS Office (Excel, Word, PowerPoint, etc.) addin. The addin is required to be written in C# or C/C++ and deployable in which end users can install it without administrator privilege.</p>
  
  <p>There are a few working example such as <a href="https://www.think-cell.com/en/" rel="nofollow noreferrer">Think-cell</a> and <a href="https://www.thomsonreuters.co.jp/ja/financial/products/tools-applications/trading-investment-tools/eikon-trading-software/eikon-download.html" rel="nofollow noreferrer">Eikon</a>. But I don't know how they archived it. </p>
  
  <p>After some research, I'm aware of the following ways to create an add-in, but none of them does not meet the requirement.</p>
  
  <h2>1. Use Visual Studio Tools for Office (VSTO)</h2>
  
  <p>It seems that installing a VSTO plugin does not require admin rights, but it needs VSTO runtime to be installed and the runtime installer requires admin rights.</p>
  
  <h2>2. Implement the IDTExensibility2 interface</h2>
  
  <p>In this case, the DLL can be placed in somewhere like <code>C:\Users\myuser\AppData\</code> without admin rights, but eventually the DLL must be </p>
  
  <ol>
  <li>registered under <code>HKEY_CLASSES_ROOT</code> as a normal COM, and</li>
  <li>registered under <code>HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\(PowerPoint|Excel|Word|Outlook|etc.)\Addins</code>.</li>
  </ol>
  
  <p>Here, the problem is the first registration requires admin rights.</p>
  
  <p><strong>So, is there any other ways to develop an office addin that does not require admin rights when installed, like Think-Cell and Eikon?</strong> </p>
  
  <p>Note: I am OK with using .NET as recent Windows 8/10 has .NET runtime pre-installed. But it seems that .NET is not required, as seen in Think-cell and Eikon, to create an addin that does not require admin rights when installed.</p>