Short answerAn IoT (or M2M) SIM is a data SIM built for devices rather than people. It usually has pooled data across many SIMs, a portal to manage each one, and often access to more than one network. Use one for fleets of devices, anything that moves, and sites where losing one network is not acceptable.
The terms overlap. M2M (machine to machine) is the older name, IoT the newer one. Both describe SIMs sold for equipment rather than phones, and the features below are what set them apart.
What makes an IoT SIM different
Pooled data
Instead of a fixed allowance per SIM, all SIMs on the account share one pool. A busy site can use more while quiet ones use less, and you pay for the total. This suits estates of meters, alarms, kiosks and routers with uneven usage.
Management portal
You can see each SIM’s usage, suspend a lost one, set alerts and limits, and often see which mast and network a device last used. That saves a site visit when something goes quiet.
Multi-network access
Many IoT SIMs use a roaming profile that lets them attach to more than one UK network. If the first network fails or is weak, the device moves to another. Router Store lists multi-network SIM cards, and we have a separate post on how multi-network SIMs behave.
Security options
IMEI locking, private APNs and fixed IPs are common on IoT SIMs, so a stolen SIM cannot be used elsewhere and devices are not exposed to the internet.
Multi-network: what it does and does not do
A multi-network SIM does not combine networks. It uses one at a time. When the connection is lost it searches for another, which can take from a few seconds to a few minutes depending on the device and settings. For truly continuous service, a dual-SIM router with two SIMs, or bonding across several connections, is the next step up.
Also check whether the SIM is steered: some suppliers prefer one network and only move to others if it fails completely, which may not help in an area where the preferred network is weak but present.
Roaming SIMs
Equipment that crosses borders, such as lorries, plant hire kit and marine equipment, needs a SIM with roaming agreements in each country. IoT roaming SIMs are priced for this and usually much cheaper than consumer roaming. See Router Store’s roaming SIM cards.
Where eSIM fits
An eSIM is a SIM profile loaded onto a chip rather than a plastic card. For IoT, the attraction is changing network remotely without visiting the device. Newer routers increasingly include eSIM; Router Store explains eSIM routers, and there is more on IoT eSIM. For the 5G side of this, 5gsim.com covers eSIM and roaming in more depth.
Low-power devices: LTE-M and NB-IoT
Battery-powered sensors often use LTE-M or NB-IoT rather than standard 4G. They trade speed for range and battery life. Support varies by network and by SIM, so check both before choosing a module. Our LTE categories guide explains the difference.
Frequently asked questions
Is an IoT SIM more expensive than a normal data SIM?
Per gigabyte, often yes. Per device, for low-data equipment, it is usually much cheaper, because you pay for a small shared pool instead of a monthly allowance on every SIM.
Can I use an IoT SIM in a normal 4G router?
Yes, as long as you enter the APN the supplier gives you. Most business routers accept any SIM.
Does a multi-network SIM give faster speeds?
No. It improves availability, not speed. It can still pick a slow network if that is the only one in reach.
What is the difference between M2M and IoT SIMs?
Mostly the name. M2M is the older industry term; IoT is the newer one. Both mean SIMs sold for devices rather than people.
Choosing SIMs for a fleet of devices? Tell us about it and we will suggest a setup. Router Store also has IoT SIM cards and M2M SIM cards.
NANick Appleby
Nick Appleby has worked in UK telecoms since 1998, starting at BT, and has spent most of that time on cellular routers, data SIMs and the antennas that connect them for business and industrial sites. He writes 4G SIM to explain how the networks and the kit actually behave, in plain English.