What you need to know about dual-SIM on the OnePlus 5

Here's what you need to know about one of the OnePlus 5's most underrated features.

There are many reasons why you might want to pick up a OnePlus 5 — the price, the clean software experience, fast performance, or the bragging rights that go with 8GB of RAM. But one of the phone's most useful features for travelers isn't being heavily advertised. OnePlus's latest phone, like earlier models, is a dual-SIM handset. And that can save you a lot of hassle — and money — if you're a frequent traveler.

Here's what you need to know.

Why use dual SIM?

Simply put, a dual-SIM phone like the OnePlus 5 lets you stay connected on two SIMs at the same time — one for 4G LTE data, the other for voice calls alone, with up to 3G connectivity support. There are a few reasons why you might want to do that. If you're a businessperson, a dual-SIM phone can allow you to stay connected on your personal and work SIMs without carrying two phones.

Stay connected on your home SIM and use data on a local SIM.

If you're traveling, a dual-SIM phone can let you stay contactable on your primary (home) phone number, while using a local SIM for LTE data. This gives you the best of both worlds — friends and family can still get ahold of you on your regular number, and you can still dial out using that number if you need to. Meanwhile, you avoid potentially expensive data roaming charges by using your local SIM for 4G LTE connectivity and local calls within the country you're visiting.

If you travel frequently between two countries, a dual-SIM setup can save you the hassle of constantly swapping out SIM cards or juggling multiple handsets. Or if you live in a country where a single carrier doesn't have good coverage everywhere, you can hop between operators at will.

Dual SIM on the OnePlus 5

Using two SIMs in your OnePlus 5 is simple enough, but there are quite a few options to get to grips with. The phone takes two nano-SIMs — it doesn't matter which slot each SIM goes in, as you can change which SIM is the primary one through software later.

Unlike its predecessors, there's a single OnePlus 5 SKU for the entire world, and the phone supports 4G LTE on 22 bands, in addition to pentaband 3G (HSPA), meaning you're good to go for just about any GSM network anywhere in the world. If you're using a second SIM in your OnePlus 5 for mobile data abroad, simply keep your home SIM where it is, and use the other SIM slot for the local SIM.

Under Settings > Sim & network you'll see various settings for each of your two SIM cards. The most important ones can be found at the bottom of that page, letting you control the default SIM for calls, texts and mobile data.

In the sub-menu for each individual SIM, you can give your SIMs friendly names for easier identification, toggle data roaming and APN settings.

How it works

Whichever SIM you select as your primary SIM will connect to data at up to 4G LTE speeds, as well as being able to make and receive calls and texts. Your secondary SIM will connect to GPRS (1G/2G) or 3G (HSPA) networks and will be used for calls and texts only. (Unlike some older dual-SIM phones, which only support GPRS for the second SIM. This means the OnePlus 5 can work in certain countries where older 2G networks have been shut down, like South Korea and Japan.

It's also worth remembering that you can only use VoLTE (4G calling) and VoWiFi (Wi-Fi calling) on your primary SIM — the one you use for cellular data.

The OnePlus 5 lets you specify the default SIM for calls and texts (in the Sim & network menu, as detailed above). If you need to change the data SIM quickly, tapping the Mobile data shortcut (look for the name of your primary network) in the quick settings area will let you toggle between SIM 1 and SIM 2 for data.

For calls and texts, OnePlus's built-in Dialer and Messages apps give you toggles for chosing whether to call or text using SIM 1 or SIM 2.

Finally, a few other things you should be aware of:

Using two SIMs in your OnePlus 5, or any dual-SIM device, will consume a little more power than a single SIM, especially in areas with weaker reception. In practice, the OnePlus 5 is a pretty efficient device with a generous battery capacity, and we haven't seen a huge difference in power draw in dual-SIM mode, even when roaming.
When using two SIMs, you'll (obviously) see two reception bars in the top left corner. The one on the left is always SIM 1, the one on the right is SIM 2.
If you disable one of your SIMs through the Settings menu, it won't connect to the network — and won't draw power — but you will see a SIM icon in your notification shade to remind you it's there.

Anyone else using dual SIMs on the OnePlus 5? Share your experiences down in the comments!