Parts pairing: why some spare parts trigger messages

Parts pairing means that a part is linked by software to exactly the device it was fitted in at the factory. When the device starts, it checks whether the part is still the same one.

If the ID doesn't match, the software reacts. That can range from an entry in Settings to a single feature no longer being available.

It mainly affects the display, battery and camera. These are the parts where you're most likely to notice the effect.

These are the most common effects. None of them makes the device unusable.

The entry in Settings is neither a fault nor a block. The device keeps working normally, charges normally and still gets updates.

When you pick it up, we show you where the entry is and exactly what it says. Then you know what a future buyer would see.

There are reasons for it that aren't just excuses. Some parts carry calibration data that only fits that one device. A camera is calibrated to its lens at the factory, and a display to its colour values.

The second reason is theft protection. If parts from stolen devices can no longer be used, stripping them for parts pays off less.

The third reason is security. With the sensors for facial recognition, it would be a real risk if third-party hardware could simply be fitted. What that means for a display replacement is covered in the article on Face ID.

So the criticism isn't aimed at the principle itself, but at the fact that it also applies to parts where none of these three reasons holds.

Apple has opened the way to using used genuine parts for repairs. Before that, many features depended on a part being brand new and assigned to the device.

On top of that, there's a repair assistant that loads the calibration data directly on the device after fitting. The step that used to need a server in the background now runs on the device itself.

One limit remains, and it makes sense: parts from devices reported lost or stolen can't be calibrated.

The European Repair Directive prohibits manufacturers from obstructing repair through hardware or software techniques. It is only allowed where there are objective reasons, such as protecting intellectual property.

The ecodesign rules for smartphones come at it from the other side: professional repairers must get non-discriminatory access to the software and firmware needed for a replacement.

Exactly where the line between an objective reason and obstruction lies will have to be settled case by case. The direction is clear. You can read more in the article on the right to repair.

For you, it comes down to three questions, and we answer them before the repair.

With some parts a notice can be avoided, with others it can't. That depends on the model and the part, and we tell you beforehand what to expect with your device.

We give our warranty on whatever we fit, regardless of whether an entry later appears in Settings.

And regardless of which spare part grade you chose. The differences the two grades make in everyday use are explained in the article on genuine and aftermarket parts.