Your phone has signal bars but no internet: what is actually wrong

First, is the phone really using mobile data?

The most common trap on a trip is Wi-Fi. If the phone has joined the hotel, café or train network, it sends everything through it, and a Wi-Fi that wants you to log in on a web page, or that simply has no internet behind it, looks exactly like a dead phone with full mobile bars. Google's own troubleshooting starts here: to make sure you are on the mobile network, turn Wi-Fi off. Its Google Fi help adds that the mobile data indicator may not show at all while Wi-Fi is connected.

iPhones abroad are more prone to this than at home. Apple's Connectivity Assist, in the Wi-Fi settings, tops up a slow Wi-Fi connection with mobile data, but Apple says it is not used while the iPhone is roaming internationally or in Low Data Mode. So a weak hotel Wi-Fi can hold on to your phone until you switch Wi-Fi off yourself. Our guide to hotel Wi-Fi or mobile data covers when each one makes sense.

Second, are the bars and the data on the same line?

On a phone with two lines, there are two sets of bars, and only one line carries data. With your usual SIM and a travel eSIM side by side, it is easy to look at the healthy bars of one while the data is set to the other. On an iPhone, Settings, Mobile Data shows which line is chosen for data; Apple's own checklist also asks you to make sure each line is turned on and, abroad, that data roaming is on for the line that carries data. On a Pixel, the choice is under Settings, Network and internet, SIMs.

If the eSIM was just installed and has never worked, the issue is set-up rather than signal; our no-service guide goes through that case step by step.

Third, is there data left on the plan?

A line that has used up its data, or whose validity has ended, usually keeps its bars. It is still registered on the network; it just is not allowed to send anything. Google's troubleshooting ends with exactly that advice: check with your carrier that nothing has changed with your data plan.

On a travel eSIM this is the first thing to rule out after a few heavy days of video calls or hotspot use. The phone's own counter shows how much the line has used since you reset it, and the provider usually shows what is left; our guide to checking data usage on a travel eSIM explains where to look and why the two numbers can differ.

Fourth, is it the network, the place or one app?

• One app fails, the rest work: the problem is that app or its servers, not your connection.
• Everything stalls in a crowd: the masts are full, as explained in our article on festivals and stadiums.
• Everything stalls in one building or underground: the signal reaching you is too weak for data even if a bar or two shows.
• Everything stalls after a VPN or a data-saving app was switched on: turn it off and try again.

Google notes that a VPN can interfere with mobile data, and the same goes for data savers that block apps in the background. The bars also do not show capacity: a crowded mast can show full signal and still leave you no room, which is why data fails at festivals and stadiums.

The reset sequence, in order

Once the checks above are done, Apple's sequence is short. Turn on Airplane Mode for at least 15 seconds, then turn it off, so the phone registers on the network again. If that does not help, restart the phone. Then, on Wi-Fi, check for a carrier settings update in Settings, General, About. On Android, Google suggests the same airplane-mode toggle and a restart.

Leave resetting network settings until last. It wipes saved Wi-Fi networks, and Google's Fi help warns that resetting mobile network settings can require reactivating the eSIM service. Ask your provider first if the line is an eSIM. If nothing works, the APN is the one setting left to look at, and the provider can confirm the right value.