(iOS + StoreKit) Can I detect when I'm in the sandbox?

After a bit of digging I found this from Apple's Technical Note TN2259:

How do I verify my receipt (iOS)?

Always verify your receipt first with the production URL; proceed to verify with the sandbox URL if you receive a 21007 status code. Following this approach ensures that you do not have to switch between URLs while your application is being tested or reviewed in the sandbox or is live in the App Store.

So it looks like I should axe the &sandbox parameter completely and just do that. I really had to dig for this answer so I'm posting it here in hopes that someone else runs across it!

I encountered that very same problem, where my app was rejected because the "production" version of my app that I submitted was hardcoded to connect to a PHP script on my server that validates receipts with the real AppStore server (whereas my development build points to another PHP script that validates receipts with the sandbox server). However, after a few exchanges with Apple engineers, I found out that they use sandboxed user accounts to tests submitted applications, which explains why they got an error.

Instead of conditionally building my app to point to one script or the other, I will use a single script that tries the production server first and then falls back to the sandbox server if it receives the 21007 status code, as explained above!

Thanks a lot!

Always verify your receipt first with the production URL; proceed to verify with the sandbox URL if you receive a 21007 status code.

Unfortunately, the technical note fails to mention this is only valid for auto-renewing subscriptions!

As the In-App Purchase Programming Guide mentions below table 7-1:

Important The non-zero status codes here apply only when recovering information about a auto-renewable subscription. Do not use these status codes when testing responses for other kinds of products.

For non-renewing subscriptions, the production server does not return a status code, but a proper receipt.

In case you are forced to use non-renewing and implement your own subscription expiring logic, a possible solution is to send your app version along to your server, and keep track of which versions are in development at the moment, as such you can redirect to the sandbox.itunes server to verify receipts where appropriate, and mimic the x-minute expiring time of a subscription (as sandbox.itunes does for auto-renewing) for development on your server.