Unlocked smartphones are smartphones which have the potential capability to be used on any wireless network, rather than being tied to a specific carrier. The advantage of purchasing unlocked smartphones is that the consumer can exercise more choice about the type of plan used, and it is also very easy to switch between carriers if different services are needed, or if the user wants to travel. The disadvantage is that the consumer usually needs to pay full retail price, in contrast with getting a steeply discounted phone in combination with a service contract from a specific network.

The practice of locking phones is designed to enforce customer loyalty by making it hard to leave a particular network. Consumers started rebelling against the practice in the early 2000s, often specifically because of the desire to change networks with a smartphone.

Locked phones are phones which have been programmed so that they can only be used with a particular provider. In some cases, the programming may be easy to reverse, with the user simply reformatting the phone or removing the phone's memory card. In other instances, the phone may be designed in such a way that it is impossible to use it with another network, with some companies manufacturing specific phones for particular networks. In contrast, an unlocked phone can be used on any carrier which permits customers to use unlocked phones.

The definition of a “smartphone” is, alas, a bit more complicated than the definition of an unlocked phone. Smartphones are cell phones which offer additional features that differentiate them from conventional cellphones. A regular cellphone usually offers voice and basic data services such as text and picture messaging. A smartphone, by contrast, may have a full keyboard, an independent operating system, and functionality which approaches that of a small computer. Smartphones are very popular with travelers and businesspeople, since they are portable and often very easy to use.

With a smartphone, carriers usually recommend a robust data plan which allows the consumer to transfer large amounts of data. Text and picture messages are comparatively quite small, while browsing the Internet, sending email, and exchanging files can eat up data allowances quickly. As a result, smartphone plans tend to be more expensive, and some consumers grow frustrated with particular providers, but want to keep their smartphone. This is where unlocked smartphones come in handy, since the consumer can drop one service plan and start another.

There are a number of sources for unlocked smartphones. Some people go directly to the manufacturer, but it is also possible to purchase unlocked smartphones through third party retailers. Some cellular providers may also offer an unlocked option to their customers, offering people the choice of getting a locked phone at reduced price with a service contract, or buying a more expensive unlocked smart phone which is accompanied with more flexibility.

It is also possible for people to unlock certain smartphones on their own, if they have computer programming skills, but this can also result in “bricking” a device, rendering it useless. Networks will usually not replace phones which have been bricked as a result of attempts to unlock, so unlocking one without experience is a risky endeavor.