John Gruber wrote a quick post titled Bad App Citizens where he says:

It’s getting to the point where most apps can’t be updated over cellular because they’re all over 100 MB. This is madness.

I decided to test out exactly how much data is transferred on some of these larger apps. I'm not super clever at monitoring Wifi data use, but I was able to use iOS's built in cellular data tracking to measure how much data was transferred for each update. Here's what I came up with:

• Total data displayed: 962 MB
• Total data downloaded: 348 MB
• Biggest difference: Google Home (99% smaller)
• Smallest difference: Netflix (20% smaller)

As you can plainly see, there is quite a range between an app's advertised size and how much data is actually transferred when you update said app. Twitter had the largest discrepancy, showing 122 MB as the app size, but downloading less than 1 MB to perform its update. Clearly the update Twitter rolled out had more impact from delta updates to thin out their update size, and the same is true of Target and Nokia Health Mate, both of which are around 100 MB total, but each downloaded just over 1 MB for their updates.

"App thinning" is not a magic bullet that erases this problem though, as Facebook Messenger, which shows as being 154 MB, still downloaded 99MB of data for its update.

Of note, Apple does not allow you to download apps or updates that are over 100 MB, and the only app update I was not able to perform was for Facebook. The Facebook app is advertised as being a whopping 251 MB app, and I don't know what the update size is, but it was over 100 MB. Has Facebook changed so much in the past 3 days since an update that it needed to replace over 40% of its code?

The internet is full of people who are both upset about these app sizes and those who think delta updates make this complaint void. I think it's important that people understand that the size you see on the Updates page in the App Store is not how much you are going to download but it's certainly not fair to say delta updates have fixed everything. Yes, they've made some updates negligible, but I burned through 348 MB of of data in one day exclusively from updating my apps. That's insane! Thankfully, I'm on an unlimited plan with T-Mobile and I'm a nerd who has turned auto-updates off so this won't break my plan.

As mentioned by Carlos Ribas on Twitter, auto updates only happen when you are connected to Wifi, but iOS won't stop you from updating on cellular if you tap the update button. The fact that someone could blow through 10% of their monthly data plan (2GB) just by updating Snapchat and Messenger once. This could be tough if you do it once, but Facebook updates Messenger all the time. They've updated the app 5 times in the past month, which could work out to upwards of 400-500 MB over just a month.

And of course, Facebook has such great release notes for each of these updates that really justify why these updates are so critical…

So are giant app sizes a problem? Yes. Do delta updates allow these updates to use less data? Yes. Do delta updates make these large apps a non-issue? Hell no!