What is SIM (Subscriber Identity Module) card?

A SIM (Subscriber Identity Module) card is a chip card that stores the IMSI and serves to identify the mobile subscriber and provide mobile service.

What is a SIM card used for?

Each SIM card holds users’ IMSI and ICCID numbers. Mobile network operators (MNO) use SIM cards, IMSI, and ICCID numbers to verify the holding user and to grant network access to the associated device.

A SIM card can serve as a memory storage device, e.g., to store contacts or SMS messages, network information, or apps particular to the mobile user’s mobile operator. This storage space, however, is relatively small (from 8 KB to 256 KB).

What is a prepaid SIM card?

A prepaid SIM card has a pre-loaded set amount of money, acting as a credit balance with the service provider. It can be used for messages, Internet browsing, calls, etc. When the balance on the prepaid SIM reaches zero, the provider discontinues service immediately, and you have to buy a new one.

What are the types of SIM cards?

Since its debut in 1991, SIM cards have had a few adaptations to their hardware leading to five main types of SIM cards:

  • Full size
  • Mini
  • Micro
  • Nano
  • Embedded (eSIM)
Oct 10th, 2019
2 min read

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