So today I was doing some SharePoint 2013 app development against my Office 365 SharePoint 2013 tenant and I needed to view the HTTP traffic from the site in order to troubleshoot some issues I was having and I stumbled across something I found very interesting when I looked at the header details in Fiddler:

Yup, that’s right – my tenant is on SharePoint 16 – not 15 which is the current public release of SharePoint. To confirm that this wasn’t just something with the headers I navigated to and there it is again:

(In case you’re wondering, the service.cnf file hard codes the version information for the current web application and if you have an on-prem version you can see it in the \_vti\_pvt folder of you local web application’s site – you can also look at \_vti\_pvt/buildversion.cnf to get the actual build number).

Another confirmation test I hadn’t thought of but James Love (@jimmywim) pointed out to me was that the page layouts within the site are also referencing assemblies. I downloaded the DefaultLayout.aspx file to confirm and this is what I see:

1<%@ Page language="C#"   Inherits="Microsoft.SharePoint.Publishing.PublishingLayoutPage, Microsoft.SharePoint.Publishing,Version=,Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

So you may be asking yourself – what does all this mean? Has Microsoft upgraded my SharePoint Online Farm to the next version of SharePoint? Well, I honestly don’t know but I think all the evidence is pretty clear that they must have. In terms of what is different, I simply couldn’t tell you as I’ve not noticed anything different – perhaps you have? If so post a comment as I’d love to know!

I personally don’t like speculating about what this means and what Microsoft is doing so for me what is important about this information is the fact that I/you might have clients or customers running on bits that are not just different due to patch levels but are in fact on an entirely different version. As I’m working on SharePoint Apps that will be sold in the App Store this type of information is critical when it comes to troubleshooting problems. So until Microsoft releases some public information about what’s up with all of this, the best we can do is keep the information handy as we work on various projects and, hopefully, keep the discussions going so that as folks discover version related differences we communicate that information to each other for our global benefit.