Many 4G/LTE and 5G compatible phones have a tiny removable sliver of plastic called a SIM – short for Subscriber Identity Module.
This little chip identifies your account to your carrier's network. (eSIM is a newer technology that do the same thing without the removability of the chip.)
The SIM card is sometimes found lurking underneath the battery of many phones or mobile hotspot devices and can be carefully slid out with a fingernail. For devices that lack removable batteries, the SIM is usually in a tiny ejectable tray that can be removed by pushing a pin carefully into a pinhole.
If you move the SIM to another compatible unlocked phone or device, you are essentially transferring your service (including your phone number) to that new device.
This can be extremely handy – you can take a SIM from a Mobile Hotspot and put it into an iPad, for example.
Or…you can keep an old beater phone around for when you are heading out into rough conditions – such as a backcountry hike or kayaking. Before you head out, just pop your SIM into the old device and you can still keep online and get phone calls, without putting your flagship expensive smartphone at risk.
Or…when you are traveling internationally, rather than paying expensive international roaming fees, you can instead get a SIM (and a local phone number) from a local cellular company, and then get online much, much cheaper.
Or...if you have a grandfathered unlimited Verizon data plan (gUDP) that must be tied to a smartphone, you can move the SIM from the phone to a mobile hotspot or tablet device to get around paying an additional fee to tether via the plan.
Sometimes your old device and your new device don't have matching SIM card sizes. This is where a SIM card adapter kit can come in handy.
Price: $2 - $10
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- T-Mobile Expands Test Drive to iPhones - Free 30 days / 30GB of Data via eSIM Activation Posted on: June 28, 2021
- Google Fi Rolls Out eSIM Support For All Customers Posted on: May 19, 2020
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SIMs have been getting smaller over the years – the original full-size SIM from the early 1990s was the size of a credit card!
But the ones you are most likely to see today are:
- Mini-SIM / 2FF (now often called "standard" or "regular" size)
- Micro-SIM / 3FF
- Nano-SIM / 4FF
They are all electrically identical – so it is actually possible to cut down a Mini-SIM to put it into a device that has a Nano-SIM slot.
And, of course, the late 20-nineteens brought the advent of the eSIM to fruition.
We have an in-depth guide to this topic in our Guide to SIM cards - check it out!
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