Background

There’s a bit of mystery surrounding whether Google Ads are blocked in China or not (as the search engine itself and many of the other main services certainly are).

You can confirm for yourself by checking the up-to-date Greatfire.org results for the following URLs:

https://www.google.com
https://www.google.com/admob (however, as this is the ‘dashboard’ URL, it may not actually be the same endpoint used by Admob ad services themselves).

How about Chinese iOS ad networks?

I went to great efforts to research iOS ad providers operating in China, as they’d be guaranteed to work. I ideally wanted to find one that allowed me to reuse the current Google Admob framework that I’d gone to the effort of setting up already: Reddit thread. However, as I report in the thread, all services seem to require a Chinese ID, and most involve getting into direct contact with the advertising agency (rather unsettling for me).

Investigation

As nobody was giving any satisfactory information on the subject, I decided take it into my own hands and make a TestFlight build of my app, LinguaBrowse, to have people test it in China. I got the help of three testers. Following the great results of the first test session, I released the app on the China App Store rather than just using TestFlight.

Evidence is documented in full in this imgur album (testers 1 & 2) … and this one (tester 3), though I’ll show some key images for flavour here anyway:

Tester 1: using an iPhone with China Telecom on my TestFlight build

Note: although this tester’s carrier says 中国移动 (China Mobile), the tester believes that the WiFi in use is actually provided by China Telecom.

My banner ad appeared in portrait mode, and was able to automatically refresh with a new ad every two minutes (although I only got a screenshot of the first one, sorry). We did not test landscape mode.
Ads appeared and refreshed regardless of whether VPN was off or on, so it gets past the Great Firewall without any ads being blocked.
Of note, we were also able to view Google AdMob ads placed by other parties on websites that we visited, so it’s not just in-app AdMob services that work, either.

*— China Telecom permitting a portrait-mode banner ad on iPhone.*

Tester 2: using an iPad with China Mobile on my App Store app

As before, my banner ad appeared in portrait mode, and was able to automatically refresh with a new ad every two minutes (this time, I do have two separate photos as proof).
I noticed later that my banner ad failed to receive ads in landscape mode (I set up my app to change the banner area’s colour to red if adView(_ bannerView: GADBannerView, didFailToReceiveAdWithError error: GADRequestError) is called). Since I only noticed this after concluding the test, I don’t have any insight into why this happened. It may be just that the available advertisers weren’t able to provide the right format of ad in time; not sure. I should note that landscape ads work just fine on an iPhone situated outside of China.
We didn’t test with VPNs.

*— China Mobile permitting a portrait-mode banner ad on iPad.*

Tester 3: using an iPhone with China Unicom on my App Store app

Portrait and landscape iPhone banner ads were blocked on China Unicom, yet worked over VPN.

*— China Unicom blocking a portrait-mode banner ad on iPhone (landscape was also blocked). Blockade was lifted immediately upon connecting to a VPN.*

Does the Google AdMob pane register any clicks?

I couldn’t test this directly, as it’s against the terms and conditions of Google AdMob to deliberately click on ads, so I had to wait a while for some data to come in. Coincident with a small number of downloads from the China App Store, Google AdMob pane does presently report (a small number of) click-throughs in China. Whether the clickers were using national Chinese internet providers (rather than VPNs), however, I don’t know; and I also don’t know whether they got their apps from the China App Store or any other nation’s App Store (not that it makes any difference, though, I expect). However, I can say that the revenue is non-zero.

Conclusion

Google AdMob works perfectly well in China for two of the three biggest ISPs (China Mobile and China Telecom), except maybe for landscape ads on iPad (requires further investigation to figure out exactly what was happening). However, it’s completely blocked on the third biggest provider, China Unicom. For the former two ISPs, I have evidence now that ads display, refresh, and that click-throughs are registered in the Google AdMob pane. Whether the eCPM is decent is a whole different question, but I’ll be watching my numbers. Hope this helps conclude a question that has been bouncing around unanswered, and with an awful lot of misinformation, since at least 2014.