SIM card
Definition
The small chip that identifies your line to a mobile carrier and links your phone to your number.
SIM card, explained
A SIM (Subscriber Identity Module) card is the removable chip that identifies your subscription to a mobile carrier. Your phone number is assigned to the SIM through the carrier's records, so moving the SIM to another phone moves your number with it. Physical SIMs come in nano, micro and standard sizes, though most current phones use nano or an embedded eSIM. A number on a SIM from a carrier is a mobile number, which is why apps trust it more than VoIP lines. Prepaid SIMs are a common way to get a second long-term number for accounts you keep.
Related terms
eSIM
A digital SIM built into your phone that lets you add a mobile line by scanning a QR code or using a carrier app.
SIM swap
An attack where someone gets your carrier to move your number to their SIM so they receive your calls and codes.
Carrier
A mobile network operator or provider that issues phone numbers and delivers calls and texts.
Where you'll meet this term
How to Receive SMS Online: Get Verification Codes Without Your Own Number
How to receive SMS verification codes online: free public inboxes vs private rented numbers vs VoIP apps vs a second SIM, with risks and setup steps.
Read the guide →Getting startedNon-VoIP vs VoIP Numbers: What's the Difference and Why It Matters for Verification
What non-VoIP numbers are, how apps detect VoIP with line-type lookups, why Google Voice and TextNow get rejected, and when each number type works.
Read the guide →Safety & privacySIM Swap Protection: What SIM Swapping Is and How to Stop It
What SIM swapping is, warning signs, and how to protect your accounts with a carrier PIN, port-out lock and 2FA that doesn't rely on SMS.
Read the guide →Getting startedWhat Is a Virtual Phone Number? VoIP, Rented SMS Numbers and eSIMs Explained
What a virtual phone number is, how VoIP numbers, rented SMS numbers and eSIMs differ, and what kind of numbers Noir SMS provides.
Read the guide →Temporary virtual number vs Prepaid SIM cardTemporary virtual number vs a prepaid SIM card
A prepaid SIM gives you a real long-term number but needs a phone slot and top-ups. A temporary virtual number covers one code online. Compare both.
See the comparison →