[mikeash]

The problematic scenario goes like this:

1. You're in a coffee shop. The WiFi sucks today. You turn off WiFi so you can use your cellular connection instead.

2. Many hours later, you go home, having forgotten about #1.

3. You binge-watch the entirety of Doctor Who streaming on your phone, not realizing the phone is still using cellular.

4. Large bill from your provider.

[hdra]

I want to see the problem solved, but this feels like the wrong solution.

Reminds me of the time where I couldn't trust what the UI says about the audio of my desktop computer running Linux circa 2005

[williamscales]

Many apps will prompt before doing a large download over data. Spotify has separate settings for mobile data and Wi-Fi streaming quality. One could imagine a video app would prompt before streaming on mobile data. I'm pretty sure this is the solution—perhaps the Android or iPhone media framework itself could implement something that would warn people if app developers are often forgetting to add this feature?

[KozmoNau7]

Android even goes too far here. "Download waiting for wifi", for a 20MB download. I use more data than that simply by opening certain apps!

[js2]

You can disallow cellular data on a per-app basis on iOS, so you could for example disable it for just Netflix.

[mikeash]

I think they're close to a good solution but not quite there. A tri-state button, where it's on/on-but-disconnected/off might have done it, or at least some indicator that "off" doesn't mean off.

[Steko]

The correct solution is "always turn on wi-fi when I get home". The phone knows when this happens, you can set reminders around it.

[planb]

No, it does not if the Wifi Chipset is disabled, because it uses wifi for location services (GPS would use way too much battery). That's exactly the problem: The wifi chipset is used for much more than just connecting to the internet.

[mschuster91]

You can also use the GSM Cell ID for this purpose. Once the user marks his/her home, grab the IDs of the surrounding cell towers and use these as trigger.

[pgeorgi]

It's exactly what my phone does (Nexus 5X with Android 8), likely by listening to wifi passively ("which SSIDs are around?")

[Sephiroth87]

That doesn't sound like a disabled chipset...

[moogleii]

Didn't iOS 10 or whichever add cellular assist to WiFi? I know some people raged about it, but I find it useful for the scenario you just mentioned.

[mikeash]

It did, but I'm not sure how well it really works. In my own experience, I still see lots of networking failures if I'm far enough from my house for the network to be dodgy but not so far that it disconnects, or if I connect to crappy public WiFi.

[KozmoNau7]

5. Realize you should have gotten a subscription with an adequate data plan.

6. Get said subscription.

7. Stop worrying.

[mikeash]

I'm not aware of any option in this country (edit: the US) that will handle massive use of streaming video. All of the plans without overage charges have a soft limit where they start throttling you.

In any case, I'm not going to pay a bunch of extra money every month just in case I forget about the WiFi.

[Tepix]

Most people don't live in countries such as Kuwait where it is normal (and affordable) to watch 4k netflix streams via LTE.

[KozmoNau7]

Kuwait? I live in northern Europe, and I have 45GB on my perfectly ordinary ~$27 plan.

[Tepix]

In Kuwait the typical mobile plan includes 1TB of traffic.

With 45GB you can watch a mere 10 hours of 4k TV per month.