Clarification of hostVersion and Office Build Version Equivalence for License Type Detection in Outlook Add-ins

Dear @Singh Rana, Devendra,

Thank you so much for contacting Microsoft Q&A Forum. 

Based on your descriptions, I can see that you want to use Office.context.mailbox.diagnostics.hostVersion to differentiate between volume-licensed and retail installations of Office 2016/2019. I also appreciate your questions related to it. Therefore, I have researched some information and here are my answers to your concern that you can consult to see if they can help you: 

1.Is hostVersion 100% equivalent to the traditional Office build/version number used to distinguish retail vs. volume licenses? 

It is not exactly. The hostVersion property in the Office JavaScript API returns the version of the Outlook client when running on Windows (classic), Mac, or mobile. However, it does not directly indicate the license type (retail vs. volume). It reflects the build number, which can sometimes correlate with the license type, but this is not guaranteed. You can take a look in this link: Office.Diagnostics interface - Office Add-ins | Microsoft Learn 

2.Can we reliably use hostVersion as the canonical source for determining license type? 

No, it may be not reliable on its own. While volume and retail builds may follow different update cadences (e.g., volume builds often lag behind retail builds), relying solely on hostVersion can lead to false positives or negatives. For example: 

• Retail builds may have higher build numbers due to more frequent feature updates. 
• Volume builds (e.g., Office LTSC) are more stable and receive fewer updates. 

Thus, hostVersion may be a supporting signal, but not a definitive indicator. 

3. Are there any edge cases or additional properties to consider?  Yes, there may have several: 

• Outlook on the web or new Outlook for Windows: In these cases, hostVersion returns the Exchange Server version, not the Outlook client version. 
• Shared environments or hybrid deployments: Users may have mixed license types across devices or accounts. 
• Activation method: The most accurate way to determine license type is via activation details (e.g., KMS for volume, retail key for retail), which are not exposed via the Office.js API but can be retrieved using tools like ospp.vbs. 

4. Is there official Microsoft documentation confirming hostVersion maps to Office build/version for license detection?  I have tried to find out it but there is no official confirmation about this matter.  Microsoft’s documentation for hostVersion only states that it returns the Outlook client version (or Exchange version in some cases), but it does not mention license type detection. You can consult in link above. 

Besides that, in this case, as a forum moderator, I have limitations in my resources and cannot access the internal databases to help you further in this interesting and complex scenario. Therefore, I highly recommend you reach Home | Microsoft Community Hub for this concern so that you can get more professional help, there will be very professional people to tell you about the steps on how to realize this function.  

Also, I hope for your understanding in this matter as I really want to help you, but I understand that it is vital for you and needs advanced advice so that I suggest you reach to them for the most efficient help. And if I have any chance to have your contribution to our forum, it can help others in our community who find the same problem, and it build our platform stronger every day.  

Wish you a pleasant day! 

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