A power cut and an internet cut feel like the same thing when you are standing in the room. The lights go, the Wi-Fi symbol goes, everything stops. But for a camera made out of an old Android phone they are almost opposite failures, and knowing which one you are having tells you exactly what is still recording and what you can still watch.
This guide is for people who do not have a perfect connection. Daily load-shedding. A broadband line that drops for an hour in the afternoon. A prepaid data pack that has to last the month. If that is your situation, the ordinary advice about home cameras is written for somebody else, and it quietly assumes two things you do not have: mains power that never stops and internet that never stops.
Here is what actually happens in each case.
What happens to a phone security camera during a power cut?
Short answer: the phone keeps recording and the router stops. The phone has a battery, so it carries on capturing video to its own storage with the screen off. The router has no battery, so the Wi-Fi network disappears the instant the mains go — which means you lose the ability to watch, but not the ability to record. When the power comes back, the footage from the dark period is already on the phone.
This surprises people. A plug-in camera and a router die together, at the same instant, because they are powered from the same wall. A phone is the only device in the setup that brought its own power supply. During a load-shedding window, the phone is the last thing still working.
You lose live view entirely — no router means no network, so nothing can reach the phone — and you lose the phone itself eventually, when its battery runs down. That last one is the real limit, and it is the one worth planning around.
You keep recording. The camera and the storage are both inside the phone, and neither needs the network. Our app writes video to the phone's own storage, so a recording that started before the cut simply continues through it.
If you already run an inverter or a small UPS, the useful thing to know is that it is worth putting the router on it, not just the phone. The phone is already covered by its own battery. The router is the thing that is missing.
Does a phone security camera still work when the internet goes out?
Short answer: yes, and more of it works than most people expect. An internet outage is a failure of your connection to the outside world, not a failure of your router. The router is still powered, still broadcasting Wi-Fi, still handing out addresses and still passing traffic between devices inside the building. So recording continues and, on most setups, so does live viewing from another phone in the same building. What you lose is the ability to watch from outside.
A home router quietly does two separate jobs, and people tend to think of it as one device doing one.
- It is a local network — a switch with an antenna, letting the devices in your house talk to each other.
- It is a gateway — the door out to your ISP and the rest of the internet.
When the ISP link fails, job 2 stops. Job 1 does not. The router is still plugged in and still running, and two phones on that Wi-Fi can still reach each other, because that traffic never needed the door.
This matters because of how the live view is delivered. Our app runs a small web server on the camera phone itself, and you watch by opening the camera phone's address in the browser of another device. That request goes from your hand, to the router, to the camera phone, and back. There is no round trip through anybody's cloud for an ISP outage to break. If you want the longer version of how that is built, we wrote it up in Embedding a Ktor web server inside an Android app, and the plain-language version is in streaming your phone's camera to another device with the screen off.
So during a broadband outage, the honest summary is: watch from inside the building, yes. Watch from your workplace, no.
The four jobs, and what each one actually needs
It is easier to reason about outages if you stop thinking of "the camera" as one thing. It is four jobs, and they have different requirements.
| Job | Needs mains power | Needs the router | Needs the internet |
|---|---|---|---|
| Recording to the phone's storage | No (phone battery) | No | No |
| Live view from the next room | No (phone battery) | Yes | No |
| Live view from outside the building | No (phone battery) | Yes | Yes |
| Streaming to YouTube Live | No (phone battery) | Yes | Yes |
Read the first row again, because it is the whole argument for this kind of camera in a place with an unreliable grid. The job you care about most — did it capture what happened — is the only job with no dependencies at all. Everything else is about convenience of viewing.
This is also why the phrase "works offline" is worth being precise about. Almost every camera app will claim it. Ask which of those four rows it means.
The part Android itself can get wrong
Android does not simply trust that a Wi-Fi network works. It probes it. The platform documentation describes a capability called NET_CAPABILITY_VALIDATED, which "indicates that the network provides actual access to the public internet when it is probed," and it is explicit that this differs from a network merely being set up for internet: NET_CAPABILITY_INTERNET "is about setup and not actual ability to reach public servers" (Android developer docs).
So when your broadband dies, your Wi-Fi is still there and still working perfectly well for local traffic — but Android now knows it is not validated. That is the "Connected, no internet" message you have seen.
Does the phone then move your traffic to mobile data? That depends on the phone, and it is less universal than the internet will tell you. The clearest official statement I could find is a Pixel setting called Auto-switch to mobile network, described as switching "from Wi-Fi to mobile data if: There's no Internet connection over Wi-Fi," and warning in the same breath that it "may result in higher mobile data usage" (Pixel Help). Two things matter there: it is a setting you turn on, not automatic behaviour everywhere, and Google documents it as a Pixel feature rather than as something every Android does.
The practical takeaway does not depend on resolving that. On the viewing phone, if local live view dies the moment your broadband does, check whether the phone has quietly started preferring mobile data. On the camera phone, leave mobile data switched off entirely — it needs none to record, and none to serve a live view to somebody in the same building.
What watching over mobile data actually costs
If you do want to watch from outside, that leg runs over somebody's data — yours, the camera's, or both. This is where a prepaid pack disappears, and the arithmetic is unforgiving.
I am not going to quote you our app's bitrate, because a bitrate is not a fixed property of an app — it moves with resolution, frame rate, scene complexity and what the phone's encoder decides to do. What I can do is show the shape of the arithmetic using a published number.
YouTube publishes recommended bitrates for live streaming. For H.264 in the "240p - 720p @30fps" bucket, the recommended setting is 4 Mbps (YouTube Help). Run that through the arithmetic:
| Sustained bitrate | Per minute | Per hour | A 1 GB pack lasts |
|---|---|---|---|
| 0.5 Mbps | 3.8 MB | 0.23 GB | about 4 hours 27 min |
| 1 Mbps | 7.5 MB | 0.45 GB | about 2 hours 13 min |
| 2 Mbps | 15.0 MB | 0.90 GB | about 1 hour 7 min |
| 4 Mbps | 30.0 MB | 1.80 GB | about 33 minutes |
Thirty-three minutes. That is what a 1 GB pack buys you at YouTube's own recommended rate for a stream up to 720p. Not a day of monitoring. Half a lunch break.
This is the single most important number in this article for anyone on prepaid data, and it points at a clear strategy: treat outward streaming as something you switch on for a few minutes when you have a reason, and treat local recording as the thing that runs all day. The recording costs nothing. The watching is the expensive part.
Two more things follow from it:
- Lower the resolution before you lower anything else. The relationship is close to linear. Halving the bitrate roughly doubles how long the pack lasts.
- Do not confuse this with the recording. Recording to the phone's own storage uses zero data, always, regardless of resolution. What it uses is storage — and storage has its own failure mode, which we covered in the microSD card is the weakest part of a 24/7 phone camera.
Measure your own data usage, do not trust anybody's estimate
Android will tell you exactly what one app used. On a Pixel the documented path is Settings → Network & internet → SIMs, then App data usage, and "to know how much data each app uses, look below the graph" (Pixel Help). Other manufacturers put it in a slightly different place, usually under Network or Connections, but every modern Android has it.
Google adds a caveat on that same page that is worth repeating: "Your phone measures the data usage shown in your phone's Settings app. Some carriers measure usage differently. We recommend checking with your carrier for its measurements and your plan limits."
Do this once, for ten minutes of live viewing, and you will have a real number for your phone at your settings. That number is worth more than any table in any article, including the one above.
A three-minute test you should run before you rely on any of this
Do not wait for a real outage to discover how your setup behaves. Simulate one, on a quiet afternoon, in this order:
- Start recording on the camera phone. Leave it somewhere it can see something that moves — a doorway, a fan, a street.
- Open the live view from a second device on the same Wi-Fi. Confirm it works.
- Now unplug the cable that goes into your router from the street — the ISP line, not the router's power. The Wi-Fi stays up. The internet is gone.
- Reload the live view on the second device. If it still works, you have just proved that your local viewing survives an internet outage.
- If it stopped, turn off mobile data on the viewing device and try again. If it works now, you have found a phone that was preferring mobile data.
- Plug the line back in. Then check the recording file. It should cover the whole period, unbroken.
Three minutes, and you have replaced four assumptions with four facts about your own equipment.
What the documentation does not tell you
I want to be straight about the limits of what I could actually source for this piece, because the gaps are real and some of them sit close to the main argument.
- Google does not document what I told you in section two. I could not find any official Android or AOSP page stating that a device stays connected to a Wi-Fi network whose internet link is down, or that other devices on that network remain reachable. The reasoning in this article comes from how routers work as network equipment, not from a platform guarantee. That is exactly why step 3 of the test above exists — you should verify it on your own hardware rather than take my word for it.
- There is no documented automatic switch to cellular on unvalidated Wi-Fi. I looked for it. The platform docs describe validation thoroughly but never state the switch as universal behaviour, and the only affirmative description I found is the opt-in Pixel setting quoted above. Anyone telling you flatly that "Android always jumps to mobile data" is going beyond the documentation.
- Android's behaviour when DHCP fails is not documented on any page I could retrieve, and neither is what happens to sockets that are already open when a network loses validation.
- YouTube does not publish separate 360p or 480p bitrates. Those resolutions fall inside a single "240p - 720p" bucket. If you see a neat per-resolution table with a distinct 360p figure, it did not come from YouTube.
- YouTube also does not document what happens when your upload bandwidth is insufficient. Its help page tells you to lower your chosen resolution yourself, and notes that moderate errors "may cause degraded quality" — but there is no official statement that it drops the stream, reduces resolution for you, or buffers.
- The per-app data screen is documented for mobile data, not Wi-Fi. I could not find an official page for a per-app Wi-Fi usage screen.
None of these gaps change the practical advice. They change how confidently anyone should state it, including me.
What to do this week
If you are setting this up in a place where the power and the line are both unreliable, the priorities are not the ones the marketing suggests.
- Put the router on backup power, not just the phone. The phone already has a battery. The router is your single point of failure for everything except recording.
- Turn mobile data off on the camera phone. It does not need it for recording or for local viewing, and leaving it on is how a data pack quietly disappears.
- Run local-only by default. Start an outward stream deliberately, for the minutes you actually want to watch from elsewhere, and stop it after.
- Run the three-minute test before you depend on the setup for anything that matters.
- Measure one session of live viewing in Android's data usage screen, and write the number down.
The general shape of the setup — old phone, screen off, recording locally, watched from another device — is covered step by step in our guide to watching a shop with an old Android phone. If more than one person needs to watch, sharing a LAN live view without an account covers what that costs you. And if you are wondering what "local-only" does and does not protect you from once several people are on the network, that is the LAN threat model.
Background Camera RemoteStream records with the screen off, stores video on the phone itself, and serves a live view from a small web server running on the phone — no account, no subscription, no credit card, and nothing that stops working because a company's servers are unreachable.
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