What Is Low Data Mode on iPhone? Does It Change eSIM Usage?

Low Data Mode is a built-in iPhone setting that stops apps from using data in the background: no automatic updates, no automatic backups, no video autoplay. It does not cap the data an app uses while you're actively in it, and it does not change how a co:sim eSIM, or any SIM, measures usage: every megabyte still counts the same, on or off. Below: what actually changes when it's on, how to enable it on iPhone and Android, and what that means for a travel data plan.

#What Does Low Data Mode Actually Do on iPhone?

According to Apple's own support page, turning on Low Data Mode changes behavior in a few consistent ways: apps stop using network data when you're not actively using them, Background App Refresh turns off, streaming quality drops for apps that support tiered quality, automatic downloads and backups pause, and services like iCloud Photos stop syncing updates. Apple's built-in apps show this concretely: the App Store turns off video autoplay and automatic downloads, Music turns off automatic downloads and high-quality streaming, Podcasts only downloads new episodes over WiFi, News turns off article prefetching, and FaceTime lowers its video bitrate.

None of that is a usage cap. If you open Maps and navigate for an hour, or stream a video you chose to watch, that data still moves, just possibly at a lower resolution for apps that adjust their own quality tier. What Low Data Mode removes is the data your phone would otherwise use without you asking it to, in the background, between the times you're actually looking at the screen.

#How Do You Turn On Low Data Mode?

Apple's iPhone User Guide documents the toggle under cellular data settings, and it applies separately to your cellular connection and to each WiFi network you join.

1. For your cellular/eSIM line: Open Settings, tap Cellular (or Mobile Data), tap Cellular Data Options, then turn on Low Data Mode.
2. For a specific WiFi network: Open Settings, tap Wi-Fi, tap the info button next to the network you're connected to, then turn on Low Data Mode.
3. On a dual-SIM iPhone (for example, a home eSIM plus a co:sim travel eSIM): open Settings, tap Cellular, tap the specific line you want to limit, then turn on Low Data Mode for that line only, leaving the other line unaffected.

#What About Android?

Android's equivalent is called Data Saver, and it behaves the same way structurally. Per Google's own Pixel support page, turning it on lets "most apps and services get background data only via Wi-Fi," while "currently active apps and services can use mobile data" normally. Enable it under Settings → Network & internet → Data Saver. The Android and iOS approaches share the same core idea: restrict what happens quietly in the background, leave what you're actively doing mostly alone.

#Does Turning It On Change What Counts Against Your Data Plan?

No. Low Data Mode changes how much data your phone chooses to use; it does not change how that usage is measured or billed by your carrier or eSIM. Every byte your phone sends or receives over cellular still counts against your plan's allowance, whether Low Data Mode is on or off. What changes is the total amount your phone requests in the first place, mainly by cutting background activity you weren't watching happen.

That distinction matters for a fixed-size travel eSIM. Turning on Low Data Mode before a trip is a genuinely useful way to stretch a limited allowance: it stops your phone from silently backing up hundreds of photos or auto-updating a dozen apps the moment it finds a weak signal, which is exactly the kind of surprise drain that empties a data-only plan faster than expected. But it will not make an hour of navigation or an hour of video calling use dramatically less data than it normally would; those are things you actively chose to do, and Apple's own list of behavior changes stops at background tasks and a handful of app-specific quality settings, not active use in general.

For travelers checking exactly how much of a plan is left, the safest reading is your carrier's or eSIM provider's own usage figure rather than a guess based on which settings are toggled on. A co:sim account dashboard shows real usage against the plan you bought, and reloadable co:sim plans, like a multi-country Europe eSIM, support adding data instantly if a trip runs longer than expected, without needing to reinstall anything. Combining that with Low Data Mode (cutting the background waste) and a sensible habit of saving heavy downloads for WiFi is a more reliable way to make a fixed allowance last than relying on the toggle alone.

#FAQ

#Does Low Data Mode make videos or calls use less data?

Partly, for apps that specifically support a lower-quality tier, but it is not a general reduction across everything you actively use. Apple's own documentation lists FaceTime as optimizing "video bitrate for lower bandwidth" under Low Data Mode, and Music turns off high-quality streaming, so those two do measurably use less data per minute with the setting on. Most third-party apps, including many video and social apps, decide for themselves whether and how to respond to Low Data Mode, so behavior varies by app and isn't guaranteed. What Low Data Mode reliably does across the board is stop background activity: automatic backups, automatic downloads, and prefetching content you haven't asked for. If you're trying to stretch a co:sim eSIM's data allowance on a trip, treat it as closing background leaks rather than a way to shrink the cost of things you're deliberately doing.

#Should I turn on Low Data Mode for my travel eSIM before a trip?

It's a reasonable default for a fixed-size data plan, and there's little downside. Turning it on for your travel eSIM line specifically (leaving your home line's settings untouched, on a dual-SIM phone) stops that line from burning data on automatic photo backups, app updates, and background refresh the moment it finds signal after a flight. It won't reduce what you actively use browsing, messaging, or navigating, so don't expect it to change the size of plan you need. If a co:sim plan is reloadable, running low mid-trip is also a smaller problem than it sounds: you can add data from the account dashboard without swapping eSIMs or reinstalling anything, so Low Data Mode is best treated as one part of stretching a plan, not the only safeguard against running out.

#Does Low Data Mode affect calls, texts, or just data?

It only affects cellular and WiFi data usage; it has no effect on standard voice calls or SMS text messages, which travel over the carrier's voice and messaging channels rather than a general data connection. This distinction matters less for a data-only eSIM like the ones co:sim sells, which carry mobile data but not a phone number, so there's no separate voice or SMS service being throttled or spared in the first place; the entire connection is data, and Low Data Mode's effect on it is exactly what's described elsewhere in this guide. On a regular phone plan with a phone number attached, you can turn Low Data Mode on or off freely without worrying that it will interfere with your ability to make calls or send texts.

Whichever mode you leave it in, checking real usage against your plan beats guessing from a setting.