Smartphone tips for international travel: roaming, data & more

Your phone is locked if it only accepts SIM cards from the carrier that sold it. If you want to use a travel eSIM or a local SIM (more on these later!) at your destination, you need an unlocked device. Unlocking is free, doesn't affect your warranty, and should be done at least a week before you travel.

Most US carriers unlock devices after 40 to 60 days of active use, provided the device is paid off. Check your carrier's website or app to request an unlock.

This is the single most important setting to check. When your phone connects to a foreign network, your home carrier bills you at international rates automatically, often before you've even unlocked your screen.

iPhone: Settings > Cellular > Cellular Data Options > toggle Data Roaming off

Android: Settings > Connections > Mobile Networks > toggle Data Roaming off

If you're using a travel eSIM as your data line, keep roaming on for that eSIM and off for your home SIM. Many travelers accidentally disable roaming on the wrong line, so double-check which SIM is active before toggling.

You have three main options, and the right choice depends on your trip length and how many countries you're visiting.

Carrier day passes: the simplest for short trips. T-Mobile, AT&T, and Verizon all offer daily passes covering 150+ countries, with rates that make sense for a few days of connectivity. Without a pass, pay-per-use rates are extremely high, so this prevents surprise charges.

Travel eSIMs: the most cost-effective for trips longer than a few days. Providers like Airalo, Saily, Holafly, and Ubigi cover 100+ countries at a fraction of day-pass rates. You install the eSIM before leaving by scanning a QR code, so data is active when you land.

Local SIM cards: these offer the best per-gigabyte rates but only available at your destination. Look for carrier stores or airport kiosks when you land, and test the SIM before leaving the shop.

Apps running in the background can burn through your data allowance without you noticing. Navigation apps, music apps, and cloud photo backups are the biggest offenders. Before you leave, disable background app refresh and pause automatic app updates and cloud backups until you're back on home Wi-Fi. Streaming video and music are the fastest ways to exhaust a data plan, so download playlists, podcasts, and shows before you travel instead.

GPS on your phone works without any data connection because it relies on satellite signals. The map data is what requires downloading. Before you leave, download maps for your destination and test them in airplane mode. An incomplete download won't help you when you're standing at an unfamiliar intersection.

Several free apps support offline maps. Google Maps lets you download specific areas by searching a city or region, tapping the three-dot menu, and selecting "Download offline map." HERE WeGo supports full country-level downloads including turn-by-turn navigation and public transit in 1,900+ cities, and it's particularly strong for driving. Organic Maps and OsmAnd are good alternatives for hikers and travelers in areas with limited coverage.

US Customs and Border Protection agents can request access to your phone at the border. There's a legal distinction worth knowing: courts have been more protective of passcode-based security (which requires you to provide information) than biometric unlock like Face ID or fingerprints (which don't). The practical takeaway is to prepare your phone in advance.

Power your phone completely off before reaching customs. Modern phones require a passcode on first boot, which gives you stronger protection than a device that's simply locked. Also disable Face ID and fingerprint unlock before you travel (on iPhone, hold the side button and a volume button for a few seconds). Use a strong alphanumeric passcode rather than a short PIN, back up your phone before you leave, and consider removing sensitive data from local storage.

These precautions apply when entering or re-entering the US and at borders in other countries with similar inspection powers.

Public Wi-Fi at airports, hotels, and cafes is convenient but risky. You're sharing the network with hundreds of strangers, and someone with basic tools can intercept unencrypted data like passwords or credit card information. A VPN encrypts your internet traffic before it leaves your device, reducing this risk significantly. Connect to your VPN before joining public Wi-Fi, not after.

A few other habits help protect you. Verify the exact Wi-Fi network name with hotel or airport staff before connecting, since fake networks with similar names are a common trick. Avoid banking apps or passwords on public Wi-Fi even with a VPN if possible. Turn off auto-join Wi-Fi in your settings so your phone doesn't connect to unknown networks automatically.

One final note: VPN use is restricted in a few countries including China, Belarus, and North Korea, so research the rules for your destination before you travel.

Before you leave, log into your carrier account and confirm whether international roaming is enabled on your line and which countries are covered. Most US domestic plans don't include international usage without an add-on, so knowing what you have matters. If you're on T-Mobile with a Magenta or Go5G plan, international data is already included at reduced speeds. If you're on AT&T or Verizon, you'll need to decide whether to add a day pass or use a travel eSIM instead.

One thing worth noting: Canada and Mexico are typically included at no extra charge on most unlimited plans, so if you're only crossing into those countries, you may not need to change anything. The FCC recommends confirming coverage and rates with your carrier before you go, so a quick call or account check now can prevent surprises later.