I am using iPhone 3gs 16gb with OS 4.0.1 and each time screen blocks it is switching from wi-fi to 3g. It comes back automatically to wi-fi each time I unblock the screen.

Can I prevent it somehow? I want it to stay connected to wi-fi all the time.

How can I check how much datas it is downloading during?

1 Answer 1


That is a feature to preserve battery life. If your iPhone is jailbroken, you can install Insomnia from Cydia to keep WiFi active while the screen locks.

If you want to check your data usage, you can go to Settings >> General >> Usage. There, you can check under "Cellular Network Data" for how much data you have used. You can reset that, then lock your screen for some time, come back and check what has changed.

Hope this helps!

  • My phone is not jailbroken :). I followed your answer and checked usage - I left phone with locked screen for a night, at the morning still no data was used - so seems it downloads nothing by itself! Thanks :)
    – Diav
    Jul 29, 2010 at 9:41
  • No prob. Glad to help!
    – Thomas
    Jul 29, 2010 at 13:49

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