Apple’s Activation Lock feature, introduced three years ago with iOS 7, is a great security feature that’s been credited with a decline in theft rates. Like any good security system, however, it can be a bit of a double-edged sword; Apple has made Activation Lock so secure that it can be a problem for users who are trying to purchase a used iPhone (or other iOS device) legitimately — if the original owner of the device forgets to turn off the Activation Lock, or doesn’t realize that they need to, the buyer can basically end up with a brick.
Fortunately, Apple has addressed this by creating a Check Activation Lock Status web portal that anybody can use to determine if Activation Lock is enabled on a specific iPhone, iPad, or iPod. To use the service, you simply need to enter the serial number or International Mobile Equipment Identity (IMEI) number of the device in question, which any legitimate seller should have no problem providing you with. After entering the serial number or IMEI (and the captcha code to prove you’re a human), the site will return a simple response showing whether Activation Lock is on or off, followed by an explanation of what this means, and what actions should be taken to deactivate Activation Lock if necessary.
Oddly, for whatever reason, the site will only return the model of the device in question if Activation Lock is enabled; when Activation Lock is off it simply returns “iOS Device.” As Apple also notes on the page, Activation Lock status can change at any time — if the device is still in somebody else’s hands, they can easily turn the feature back on. In most cases, however, if you see that Activation Lock has been turned off on a device that you’re considering purchasing (and of course you’re certain you’ve been given the correct serial number or IMEI), it’s more likely you’re dealing with a legitimate seller; there is no reason why somebody should be unable to turn off Activation Lock on their own device before selling it.