If you have ever tried to switch carriers and found that your phone would not work with the new SIM, you have probably run into a locked phone. Locking is common in the US, especially when you buy a phone through a carrier deal. Understanding how it works can save you time and frustration when you want to change plans.

This guide is written as of October 2026. Carrier policies change, so always check the current unlocking policy on your carrier's official website.

What a locked phone is

A locked phone is set up to work only with one carrier's network. If you insert a SIM card or add an eSIM from a different carrier, it will not connect, or it will show a message saying the SIM is not supported.

Carriers often lock phones they sell, especially when the phone is discounted or financed. The lock helps the carrier make sure the phone is paid for before it can be used elsewhere.

What an unlocked phone is

An unlocked phone can be used with any compatible carrier. You can switch carriers without buying a new phone, use a local SIM when travelling abroad or sell the phone more easily later.

You can get an unlocked phone in two main ways:

  1. Buy it unlocked. Many phones are sold unlocked directly by manufacturers and some retailers.
  2. Unlock a carrier phone. Once you meet your carrier's conditions, you can ask for the phone to be unlocked, or in some cases it unlocks automatically.

How to check if your phone is locked

The method depends on your phone.

  • iPhone. In many recent versions of iOS, the settings show whether there is a carrier lock. Look in the general settings, under the about section, for a line about carrier lock or SIM restrictions.
  • Android. Options vary by manufacturer. Some phones show the status in the network or SIM settings. Another way is to try a SIM from a different carrier and see if it connects.
  • Ask your carrier. Your current carrier can tell you whether your phone is locked and whether it qualifies for unlocking.

Typical unlocking conditions

Each carrier sets its own policy, but common conditions include:

  • The phone is fully paid off, or the financing agreement is complete.
  • The phone has been active on the carrier's network for a set period.
  • Your account is in good standing.
  • The phone has not been reported lost or stolen.

Some carriers unlock eligible phones automatically once conditions are met. Others require you to make a request through their website, app or customer service. Policies can differ between prepaid and postpaid customers, so read the version that applies to you.

Unlocking and phone deals

If your phone came with a deal paid as bill credits, unlocking it may require paying off the remaining balance. Remember that paying off early can mean losing remaining credits. Before you request an unlock, check what you owe and what you would lose. Our guide to reading phone deals explains this in more detail.

Compatibility still matters

An unlocked phone is not automatically compatible with every network. Phones support specific network technologies and frequency bands. Most recent phones work across the major US networks, but older or international models may not support everything. Before switching, use your new carrier's compatibility checker, which usually asks for your phone's IMEI number. You can usually find the IMEI in your phone's settings.

Buying a used phone

If you buy a used phone, check:

  • Whether it is unlocked, or locked to a carrier you plan to use.
  • Whether it is fully paid off.
  • That it has not been reported lost or stolen. Some carriers and independent services let you check an IMEI number.

Buying from a reputable seller with a return policy gives you extra protection.

Why unlocked can be worth it

An unlocked phone gives you flexibility. You can take advantage of a better plan from another carrier, use a prepaid plan for a while or use a local SIM or eSIM when you travel internationally. If you like to shop around, buying unlocked or unlocking as soon as you are eligible can make changing carriers much easier.

Know your status

Whether your phone is locked shapes which plans you can choose. Check your status in your settings or with your carrier, understand the unlocking conditions and confirm compatibility before you switch. A few minutes of checking can save a lot of hassle later.