- Definition
- Qi is the baseline wireless power transfer specification published by the Wireless Power Consortium, defining how a transmitter and receiver negotiate power and how inductive charging is kept safe and interoperable.
This page defines the term. For what it means in practice, see Qi2 explained: what the magnetic profile changes in practice.
What it covers
Qi defines the inductive coupling between a charging pad and a device, the communication protocol they use to negotiate power, and the safety behaviours required during a charging session. It is a specification, not a product: a manufacturer designs to Qi, and then has a product tested if it wants to use the Qi mark.
The specification is developed by the Wireless Power Consortium, an open standards body founded in 2008. Qi itself was published in 2010 and has been revised repeatedly since.
Why interoperability is the point
Qi is the reason a phone from one manufacturer charges on a pad from another. Before it, wireless charging was largely proprietary, and a pad that worked with one handset would not work with the next.
Qi, Qi2 and the profiles
Qi and Qi2 are not alternatives. Qi2 is the current generation of the same specification, and it introduces a magnetic attachment profile alongside the existing inductive profiles. The two profiles within the family — baseline and magnetic — are defined separately, and a product certified against one is not automatically certified against the other.
A caution on terminology
"Qi compatible" and "Qi certified" mean different things, and the difference is not cosmetic. Compatible means the manufacturer has designed the product to work with Qi devices. Certified means a sample has been tested and the manufacturer holds a licence to use the Qi mark. If a specification sheet does not say which one it means, ask.