Mobile data: what is it and how do you use it well?

Definition: mobile data is internet access provided by your mobile carrier through its network, with no modem or Wi-Fi router, unlike your home internet connection.

The terms “mobile data” and “cellular data” mean exactly the same thing. Apple uses “Cellular Data” in iPhone Settings, a reference to the network's “cells”, meaning the areas covered by each cell tower. On Android, Samsung included, it's usually called “Mobile data”. You'll also come across “mobile internet” or “cellular internet”: same idea.

Mobile data isn't just for smartphones: a tablet, a smartwatch or a laptop with a SIM card or an eSIM can use it too.

Mobile data is measured by the amount of data exchanged:

• 1 MB (megabyte): a few lightweight web pages;
• 1 GB (gigabyte): a little under an hour and a half of standard-quality video;
• 20 GB or 100 GB: a typical monthly data allowance on a plan.

Is 1 GB 1,000 or 1,024 MB? Strictly speaking, under the International System of Units, 1 GB = 1,000 MB. But many devices and carriers count in base 2, with 1 GB = 1,024 MB (which is actually a gibibyte). The gap is about 2%: it changes nothing in how you use your phone, but it explains why two counters don't always show the same number.

Mobile data works as a round trip. When you open a page or an app, your phone splits your request into small data packets and sends them by radio waves to the nearest cell tower. The tower passes them on to your carrier's network, which routes them over the internet to the service you asked for. The response travels back the same way, in a fraction of a second.

To use mobile data, you need three things:

1. a phone or device that works on the mobile network (for an eSIM, here's how to know if your phone is compatible);
2. an active SIM card or eSIM, which identifies your line with the carrier;
3. a cell phone plan that includes data, or a data-only plan.

Volume (in GB) is the amount of data you use. Speed (in Mbps) is how fast it travels. 3G, 4G and 5G refer to the network generation, and therefore to the speed and responsiveness of the connection, not the amount of data on your plan. With 5G, you download faster and latency (the response delay) drops, but 1 GB is still 1 GB.

The real speed of your mobile data depends on several factors: the coverage area you're in, the number of people connected to the same cell tower, your device and the technology available locally. When speeds plummet downtown on a concert night, it's often a sign of an overloaded tower.

Mobile data is used for anything that needs the internet when you don't have Wi-Fi. In practice, it lets you:

• send messages and make calls on WhatsApp, FaceTime, Telegram or Messenger;
• find your way with Google Maps, Waze or Apple Maps;
• browse the web (the most common use) and check your email;
• use social media (Instagram, TikTok, Facebook);
• stream music or videos;
• book a ride or reserve a table at a restaurant;
• pay or check your bank account from an app;
• work remotely or join a video call;
• share your connection with a laptop or a tablet.

On the other hand, regular calls and texts go through your carrier's phone network and don't use mobile data.

When mobile data is on, an icon appears at the top of your screen, next to the signal bars. It shows the type of network your phone is connected to. If you only see Wi-Fi, or nothing at all, you're not using the mobile network.

The exact labels vary by brand, model and country. If you see a small airplane icon, that's Airplane Mode: all radio connections are off.

The difference between Wi-Fi and mobile data comes down to where the connection comes from: a router plugged into a fixed line (fiber, DSL) on one side, your carrier's cellular network on the other, which follows you everywhere but draws on your data allowance.

Your phone decides on its own: as soon as a known Wi-Fi network is in range (your home Wi-Fi, for example), it uses it; otherwise it switches to mobile data. It can also use data while you're connected to Wi-Fi. On iPhone, Wi-Fi Assist (in iOS 27, the option has been renamed and is now in “Settings” > “Wi-Fi”) switches to the cellular network when Wi-Fi is too weak; on Android, an automatic switching option does the same thing.

Leaving mobile data on all the time is convenient, but not always smart.

When should you turn mobile data on?

Turn mobile data on whenever you need the internet without reliable Wi-Fi:

• on the go, for GPS navigation and messaging;
• to get real-time notifications (messages, emails, alerts);
• to pay, book or order from an app;
• when the Wi-Fi at your hotel or a café is too slow or not secure;
• abroad, with a travel eSIM, to use your travel data plan without roaming charges.

Why should you turn mobile data off?

There are four good reasons to turn off mobile data:

1. Avoid background usage: some apps sync, download or refresh content even when you're not using them.
2. Save battery: constantly searching for a network drains power, especially when coverage is weak.
3. Protect your plan: when your data allowance is running low, turning off mobile data avoids overages or reduced speeds.
4. Avoid charges abroad: outside the area your plan covers, roaming can cost you a lot in just a few minutes.

To turn on mobile data, all it takes is a switch in Settings. The path depends on your operating system (iOS or Android) and, on Android, on the brand: follow the steps for your device.

Turn on mobile data on iPhone and iPad

1. Open “Settings”.
2. Tap “Cellular” (or “Mobile Data”, depending on your region).
3. Turn on the “Cellular Data” switch: it turns green.

On a dual SIM iPhone, first select the line that uses data under “Cellular Data”, then turn the option on. Only one number can use mobile data at a time.

Turn on mobile data on Android and Samsung

On a Samsung Galaxy:

1. Open “Settings”.
2. Tap “Connections”, then “Data usage”.
3. Turn on “Mobile data”.

On a Google Pixel and most recent Android phones:

1. Open “Settings”.
2. Tap “Network & internet”, then “Internet”.
3. Tap your carrier and turn on “Mobile data”.

Menu names vary by brand (Samsung, Xiaomi, Google Pixel, Oppo) and Android version. If you can't find it, use the search bar in Settings to look up “mobile data” and go straight to the right menu.

The shortcut: Control Center and Quick Settings

Even faster, from the Home Screen: on iPhone, swipe down from the top-right corner of the screen (or up from the bottom edge on an iPhone with a Home button) to open Control Center, then tap the cellular data icon (the antenna). On Android, swipe down from the top of the screen and tap the “Mobile data” icon in Quick Settings. A colored icon means data is on.

To turn off mobile data, follow the same path you used to turn it on and flip the switch off: “Cellular” on iPhone, “Data usage” on Samsung Galaxy, “Network & internet”, then “Internet” on Pixel. The Control Center or Quick Settings shortcut works too.

Once mobile data is off, you still have calls and texts. However, every app that needs the internet (messaging, GPS, social media) stops working away from Wi-Fi.

Turn off mobile data for a single app

You don't have to turn everything off. You can stop a data-hungry app from using your mobile data and leave the others alone.

• On iPhone: in “Settings”, then “Cellular”, scroll through the list of apps and turn off the ones that shouldn't use data (for example Netflix or a photo app that backs everything up).
• On Android: turn on Data Saver (“Settings”, then “Network & internet”, “Data Saver”) and choose which apps keep access under “Unrestricted data”.

Tracking your mobile data usage helps you avoid surprises at the end of the month. Your phone and your carrier both show a counter: the first tells you what you've used, the second what you have left.

Track your mobile data usage on iPhone

In “Settings”, then “Cellular”, your iPhone shows usage for the current period and a breakdown app by app. System services (updates, iCloud) have their own line. To start from zero at the beginning of your billing cycle, tap “Reset Statistics” at the very bottom: your iPhone doesn't do it on its own.

Track your mobile data usage on Android

On a Pixel, go to “Settings”, then “Network & internet”, “Internet”, and tap the settings icon next to your carrier. Total usage shows at the top, and “App data usage” breaks it down app by app. In “Data warning & limit”, you can also:

• set a data warning: an alert lets you know when you reach it, without cutting anything off;
• turn on a data limit: this feature turns off mobile data once the limit is reached.

On a Samsung Galaxy, the same options are under “Connections”, then “Data usage”.

Track your usage with a data tracking app

Data usage apps, free or paid on the App Store and the Google Play Store, bring your mobile data and Wi-Fi management together in one dashboard, with custom alerts. They're handy if you manage several lines, but the tools built into your phone are enough in most cases.

Track your usage with your carrier

The most reliable counter is still your carrier's, since they're the ones billing you. Most carriers show this information (data used and remaining) in their app and in your online account, and send a notification when you're getting close to your plan's limit.

Track your mobile data usage while traveling with voilà eSIM

When you travel with a voilà eSIM, you track your usage in real time in the voilà eSIM app: remaining data and how long your plan is valid.

What uses the most mobile data is video. An hour of a show in HD uses dozens of times more data than an hour of music. The most data-hungry uses are:

• video streaming (Netflix, YouTube, Disney+, Prime Video), especially in HD and 4K;
• short videos and stories (TikTok, Reels, Instagram Stories), which play automatically;
• video calls (FaceTime, WhatsApp video, Teams, Zoom);
• online gaming and game downloads;
• automatic updates and cloud backups (photos, videos), which run in the background.

Text messaging, emails without attachments and GPS use very little in comparison.

How much mobile data does each app use?

Here are ballpark figures per hour of use, based on official numbers from the services themselves and from Orange:

Lowering video quality is the single move that saves the most data: going from HD to standard quality cuts usage roughly fourfold.

Does a personal hotspot use mobile data?

Yes. When you share your connection with a laptop or a tablet, every data transfer from the other device goes through your mobile data. And a computer often uses more than a phone: system updates, cloud syncing, full desktop versions of web pages. Remember to turn off your computer's automatic updates before connecting it to your phone. Good news when you travel: using your phone as a hotspot is included in every voilà eSIM plan.

How many GB of mobile data you need per month mostly depends on how much video you watch. To see where you stand:

To give you a concrete idea, Orange says 5 GB covers about 8 hours of video calls per month, and 30 GB about 42 hours of standard-quality video. With only 100 MB, you're limited to messaging and a few lightweight web pages.

Average usage goes up every year with video and 5G: active 5G users consume noticeably more data than 4G users. Before switching plans, check your actual usage over the last three months in your phone's settings.

These benchmarks apply to your usual plan. For a trip abroad, you work out what you need differently, based on the number of days and what you'll do there: our page on how many GB for your trip gives you a quick estimate.

Day to day, a few settings are all it takes to manage your mobile data usage:

• Turn on Low Data Mode on iPhone: “Settings”, then “Cellular”, “Cellular Data Options” (and “Data Mode” on a 5G plan), then “Low Data Mode”. It pauses background refresh, lowers streaming quality and stops automatic downloads and backups.
• Turn on Data Saver on Android: “Settings”, then “Network & internet”, “Data Saver”.
• Turn off video autoplay in Instagram, Facebook, X and the App Store.
• Adjust streaming quality: standard-quality video and normal-quality music on the mobile network, in each app's settings.
• Set app and system updates to Wi-Fi only.
• Limit photo and video backups (iCloud, Google Photos) to Wi-Fi.
• Download what you'll watch or listen to ahead of time: shows, playlists, podcasts.
• Turn off Wi-Fi Assist or automatic switching if your plan is small.

Yes, you pay for mobile data, but you've already paid for it: it's included in your cell phone plan, as a GB allowance that renews every month. As long as you stay within that allowance, you don't pay anything extra.

What happens when you go over depends on your plan:

• your speed is heavily throttled until the end of the month: you stay connected, but very slowly;
• your carrier offers you a paid top-up of a few GB;
• on some plans, overages are billed per MB, which can add up fast.

Either way, calls and texts keep working. The smart move: set an alert at around 80% of your allowance and check your carrier's app to see how it handles overages.

When your mobile data isn't working, the cause is often simple. Check in this order:

1. Mobile data is turned off: check the switch in Settings or in Control Center.
2. Airplane Mode is on: it cuts all radio connections.
3. Your plan has run out, or a data limit set on Android has cut the connection.
4. You're in an area with no coverage (basement, mountains, remote countryside).
5. The wrong line is selected on a dual SIM phone.
6. Your network settings are wrong, especially the APN (the access point that connects your phone to the internet).
7. Abroad, data roaming is turned off.

Point 7 is the most common issue with a travel eSIM: the eSIM runs on the network of a local partner carrier, so your phone treats it as roaming. You need to turn on data roaming for the eSIM line (see below), or nothing gets through. Our article on how to install an eSIM walks through the settings.

If nothing works, restart your phone, then reset your network settings as a last resort (you'll have to re-enter your Wi-Fi passwords). If the problem persists, or if an error message appears, contact your carrier's customer service: an agent can check your line.

The charges for mobile data abroad depend on where you travel. Using your plan outside your home country is called roaming: your phone connects to a local carrier's network, which bills your carrier, which then bills you.

In the European Union, the “Roam like at home” rule has applied since June 15, 2017: you use your plan at your home country's rates, with no extra charges. It also covers Iceland, Liechtenstein and Norway and, according to the European Union, Moldova and Ukraine. A fair use limit exists to prevent permanent roaming.

Outside that zone, it's a different story: roaming charges apply, data is billed per MB or through travel passes on the foreign network, and the bill climbs very quickly. Even in Europe, watch out on a ship or a plane: if your phone connects to a satellite network, EU rules no longer apply and rates aren't capped. For country-by-country details, check out our article on roaming in Japan, for example.

Heading to North Africa instead? Carrier offers and their rates are compared in our article on roaming in Morocco.

Turn on mobile data abroad

To use your mobile data abroad, your phone has to allow roaming:

• On iPhone: “Settings”, then “Cellular”, “Cellular Data Options”, and turn on “Data Roaming”.
• On Samsung Galaxy: “Settings”, then “Connections”, “Mobile networks”, and turn on “Data roaming”.

Only turn it on for the line that should use data abroad: your travel eSIM, or your usual line if your plan covers the destination.

Yes, mobile data works without a physical SIM card, thanks to eSIM. An eSIM is a chip built into your phone: instead of inserting a plastic card, you download an eSIM profile that holds your plan. You can even keep your usual SIM card and add a data eSIM alongside it.

Each eSIM chip has its own identifier, the EID number, but you'll almost never need to know it.

To understand the technology inside out, see what is an eSIM, where we cover it in detail.

Before you buy, make sure your phone is compatible: most recent smartphones are, and the full list is on our eSIM compatible devices page.

When you travel, managing your mobile data is mostly about keeping your usual plan from racking up sky-high roaming charges.

Turn off roaming on your usual line

Before you leave for a destination outside the area your plan covers, turn off data roaming on your usual line. You still get calls and texts, but your plan stops using data abroad. Some apps exchange data as soon as a connection exists, even if you don't open them: turning off roaming is the only real guarantee.

Dual SIM: choose the line that uses mobile data

With a dual SIM phone, you can keep your usual line for calls and texts, and run all your data through a travel eSIM. On iPhone, go to “Settings”, then “Cellular”, tap “Cellular Data” and choose the eSIM line. Leave “Allow Cellular Data Switching” turned off: otherwise, your usual line can use data during a call and end up roaming.

Wi-Fi, Airplane Mode and offline content

Free Wi-Fi at your hotel or a café is a good complement to the mobile network, but it's often slow, and an unsecured public network offers no privacy or protection for your data: no checking your bank account on it. Also think about offline maps. And if you want zero risk, combine Airplane Mode and Wi-Fi: you turn only Wi-Fi back on, and your usual line stays silent. For a group or a long stay, pocket Wi-Fi is another option: we compare it to eSIM in our article on pocket Wi-Fi in Japan.

Compare the options for getting mobile data abroad

You have four options for getting mobile data abroad. For a concrete example in one destination, our article on internet in Japan compares them on the ground.

Travel with a voilà eSIM

With voilà eSIM, the problem is solved before you even leave. You pick your destination in the app, buy a data plan from 1 to 50 GB, from $0.90 depending on the destination, and the price shown is the final price: no subscription, no roaming charges. voilà eSIM covers more than 200 destinations, with 5G where it's available locally.

The three reasons travelers choose it:

• excellent value for money, with a plan that fits your trip instead of an overpriced carrier pass;
• an easy-to-install eSIM, set up in two minutes, and an easy-to-use app to track your data in real time;
• 24/7 human customer support, reachable on WhatsApp wherever you are.

You keep your usual line for calls and texts. For a trip around the world, the Global eSIM covers you in several countries with a single plan.