Where is Windows 8's "package cache" for store applications?

I would like to mess around with a few applications on the Windows Store. The only problem is that I don't know how to obtain the .appx file that is Windows 8's package format.

I know it has to save it's packages somewhere before installing them. Where are they, or how can I download .appx files directly from the Windows Store without installing?

The appx file ends up inside C:\Windows\SoftwareDistribution\Download\<HashCorrespondingToApp>\. My tests show several files, with no obvious way to combine them, though the largest one may be unpackable as an appx file - I have not tried that.

It is probably easier to grab the files directly from Microsoft's website. To do this I have used Fiddler to intercept download requests from the Windows Store to figure out the download URL. Note that if the app has been downloaded/installed before, it will not be downloaded again. You could try deleting the folder described above, but be careful and do so at your own risk - I have not tested that.

1. Download and install Fiddler4

2. Download and install the EnableLoopback Utility (see here for more info) to enable capturing of Modern UI app traffic

3. In the EnableLoopback tool, tick Store and click Save Changes

^{Click for full size}

4. Start Fiddler. You may wish to stop capturing (File => uncheck Capture Traffic) until you are ready to install the app, and then stop right after, to reduce clutter. Make sure you are capturing before you click Install. You may wish to test by loading a Store page, and seeing if anything is captured.

5. Click Install on the app page in the Store.

6. As you can see in the screenshot, on the left we have Microsoft's BITS downloader downloading the file in, well, several bits. Click on one of the requests, and take a look at the Inspectors => Headers tab on the right. You should see a request string starting with HEAD or GET (click inside to wrap), and with a path ending with .appx, probably followed by a query string (starting with a question mark, ?). You need the highlighted part (i.e. from just after HEAD or GET up until just before HTTP/1.1).

You also need the Host, in this case aq.v4.a.dl.ws.microsoft.com. Combine them like so: aq.v4.a.dl.ws.microsoft.com/dl/content/b/6/updt/2012/08/21<snip>826.appx?P1=13<snip>%3d (I've snipped some parts, since I'm pretty sure the download link is linked to your Microsoft Account). You can then use your favourite web browser to download the file. Note that the link only lasts for a limited time, so don't bother saving it.

^{Click for full size}