My iPhone 4 data usage suddenly spiked. From using 30-40% of my monthly allowance in the average month (3-400Mb out of a allowed 1Gb), recently I used 175% (1.75Gb) in a single day.

I have to assume that they numbers from my carrier are more or less correct. The figure shown in Settings > General > Usage more or less tallies with their report.

There are a few apps (DataMon, etc.) which will monitor usage as a whole, but I'd like an app which can break down my usage by which app is consuming the data. (Ideally 3G vs Wifi too.)

Does anything like this exist - or can it even exist? My iOS coding skillz are not strong, and I can't think how I could do this, but that certainly does not mean that no-one else can.

NB. I'm not too concerned about challenging the figure, I trust it to be reasonably correct based on past performance, but I'd quite like to be able to monitor the apps and decommission those which seem to be using a disproportionate amount.

2 Answers 2


I know this doesn't answer the question specifically, but are you sure you are on wi-fi when its available and not just solely on 3G? I've made that switch in the past and forgotten to go back. Also, have you installed any apps recently around the time the spike occrured?

  • It normally switches back to wifi (a far amount of the usage occured while I was at home and I should have expected to be using the home wifi). Does an open connection switch to a new source? E.g. if an app is consuming 3G, but then the unit detects a wifi connection, does the app switch away from 3G?
    – Unsliced
    Dec 13, 2010 at 16:54
  • Switching is done entirely at the OS level; apps don't care how they get data just as long as they have a connection. Dec 13, 2010 at 16:56

Onavo (available via iTunes) is a great app to monitor and breakdown your usages, it displays data usage by app and compressed data over 3G.

EDIT: The primary goal of this app is to reduce data volume by routing all traffic through Onavo's servers and compressing the data between the phone and the server. Depending on your privacy needs this may not be acceptable for you.

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