Why mobile data gets unreliable indoors

Your phone shows bars indoors, but pages pause, messages take time to send, or a call breaks up. Mobile data can become less reliable inside a building even when it works normally outside.

Walls and windows can weaken cellular signals, and your phone may switch between network bands or nearby cell sites as you move. Use the Connection Stability test to see whether requests are dropping or slowing down, then compare results in different locations.

Test mobile data indoors

1. Open the Connection Stability test on your phone. In your phone's Settings, turn Wi-Fi off so the test uses mobile data. If you use two SIMs, check which one is selected for data.
2. Stay in the spot where you notice the problem. Run the test for a few minutes without moving the phone, and note the response time, jitter, lost requests, and any dropouts.
3. Repeat the test near a window or outside the building. Keep the phone in the same orientation and use the same SIM, if possible.
4. Compare the results at another time of day. A separate test during a busy evening can help reveal whether the issue changes with network demand.

For a fair comparison, avoid downloading large files or streaming video during the tests. If you use a VPN, test with it both on and off, but only if your work or safety rules allow you to disconnect it.

What the result means

The test is steady indoors and pages still fail

If response time stays consistent with no lost requests or dropouts, the mobile connection may not be the cause. The problem could be limited to one app, website, or service. Try another app or site, and check whether the same problem happens with Wi-Fi.

The test is poor indoors but improves near a window or outside

The building is likely reducing the cellular signal. Concrete, metal structures, coated or low-emissivity windows, and underground rooms can all make it harder for a phone to reach a cell site. Moving closer to an exterior wall or window may help, though the best spot depends on the building and nearby network equipment.

The test is poor indoors and outdoors

This points to a broader issue, such as congestion, a carrier outage, a plan or SIM problem, or trouble with the phone's network connection. Repeat the test later and compare with another phone on the same carrier, if one is available.

Results change sharply from one run to another

Your phone may be switching between network bands or cell sites, or the network may be busy at that time. Jitter is variation in how long requests take. A few lost requests or a brief dropout matter more for calls and live meetings than one isolated slow response.

How to improve the connection

1. Try a different position. Move toward a window or an outside wall, then wait a minute and test again. A small change in position can help, but signal reflections inside a building can also make one nearby spot worse than another.
2. Reconnect to the mobile network. Turn Airplane Mode on for about 10 seconds, then turn it off and wait for the phone to reconnect. This can prompt a fresh connection, but it will not overcome a weak signal or a busy cell site.
3. Check that mobile data is enabled for the right SIM. On an iPhone, open Settings › Cellular and check Cellular Data and the selected line. On Android, open Settings › Network & internet and check the SIM or mobile network settings. Menu names vary by phone maker.
4. Compare 5G and LTE settings. In some places, one network type is more stable than another. On an iPhone, look under Settings › Cellular › Cellular Data Options › Voice & Data. On Android, look under Settings › Network & internet for your SIM's preferred network type. Try another available option, test it, and restore your usual choice if it does not help.
5. Check for a carrier or account issue. Confirm that your plan has data available and that the carrier has no reported outage. If other people on the same carrier have trouble in the same place, the issue may be with local coverage or network capacity.
6. Restart the phone and install pending updates. A restart can clear a temporary network problem. Check for phone software and carrier settings updates, then repeat the same test in the same spot.

What the test can and cannot tell you

A browser cannot read your phone's cellular signal strength in dBm, a unit used to describe radio signal power. Bars are also a rough guide, not a direct measure of how quickly a web request will finish. The Connection Stability test measures the connection's behavior, including response time, jitter, lost requests, and dropouts. It does not identify whether a bad result came from building materials, tower congestion, a carrier issue, or a phone setting.

For that reason, compare results rather than relying on one run. If mobile data is consistently unreliable in one building but works elsewhere, ask your carrier about coverage at that address and whether it offers an approved indoor coverage option.