Definition: SIM card

(Subscriber Identity Module card) A smart card that gives a cellphone or satellite phone its identity. Along with other data, the SIM card includes the carrier name, country code, dialing numbers and network authentication code (see IMSI). Introduced in 1991 for GSM phones, most SIM cards are removable. If users change phones and remain with the carrier, the SIM card can generally be moved to the new phone.

For travelers with unlocked phones, prepaid SIM cards are available, and phones that hold more than one SIM are also offered (see multi-SIM). In the early 1990s when cellphones were large, the first SIMs were the size of a credit card. However, SIM cards are increasingly being replaced by a built-in chip (see eSIM). See SIM lock, R-UIM and smart card.

Mini, Micro and Nano SIM Cards

A SIM is a chip with contacts on cardboard. During the transition to Micro cards, Micro SIMs were placed in a Mini SIM form factor (right).

                  Size    Thick   Form
  SIM Card         (mm)    (mm)   Factor

  Full Size        86x54   .76     1FF
  Mini             25x15   .76     2FF
  Micro            15x12   .76     3FF
  Nano             12x9    .67     4FF
  Embedded          6x9   up to 1

Mini SIM

This Mini SIM was removed and flipped over to show the contacts that press against the pins in the slot.

Open the Case or Slide Out the Tray

Access to a SIM card is either from the inside by taking the back off the phone or by inserting a pin into the side of the phone that releases the tray. See SIM needle.

Prepaid SIM Cards

For travelers with unlocked Android and other GSM cellphones, prepaid SIM cards can be purchased.

Mini or Micro

A SIM card may come in both Mini and Micro SIM formats that can be punched out as required.