The number printed on a wireless charging pad is a ceiling, not a promise. Getting the speed it advertises depends on four things lining up at once, and most people only ever check one of them. Here's how the whole chain works.
The short answer: to charge at 25W you need a phone that supports it, a certified Qi2 25W pad, a wall adapter rated 30W or higher, and nothing thick or metal between the coils. Miss any one and the system quietly falls back to a slower speed.
What's physically happening
Wireless charging is magnetic induction over a very short distance. A transmitter coil in the pad produces an alternating magnetic field; a receiver coil inside the phone converts that field back into electrical power. The two devices talk to each other to regulate output and detect anything abnormal.
The consequence of that mechanism is the thing everyone eventually discovers: alignment matters enormously. Poor alignment wastes energy, slows charging and generates heat. That single problem is what the last few years of standards work has been about.
What's the difference between Qi, Qi2 and MagSafe?
| Standard | Arrived | Max power | Alignment |
|---|---|---|---|
| Original Qi | 2010s | Up to 15W | None, coil placement by hand |
| MagSafe | 2020, iPhone 12 | 15W, later 25W | Magnet ring, Apple's own |
| Qi2 | 2023 | 15W | Magnetic Power Profile |
| Qi2 25W (Qi2.2) | 2025 | 25W | Magnetic Power Profile |
Original Qi relied entirely on coil placement with nothing to help you get it right. This is why phones would sit on a pad overnight having slid a few millimetres off, and barely charge.
MagSafe arrived with the iPhone 12 in 2020 and solved alignment with a ring of magnets around the coil.
Qi2 came from the Wireless Power Consortium in 2023 and added the Magnetic Power Profile, bringing MagSafe-style magnetic alignment into the open standard. This is why a magnetic iPhone case snaps onto a Qi2 charger exactly as it does onto a MagSafe one.
Qi2 25W, also called Qi2.2, was finalised in 2025 and raises the ceiling to 25W, roughly 70% more power than the original Qi2 level, alongside better thermal control and tighter alignment.
The distinction worth holding onto: MagSafe is Apple's branded implementation and accessory ecosystem. Qi2 is an open certification standard. They use the same magnetic alignment approach but they aren't interchangeable terms.
The four things that must line up for 25W
A phone that supports it. As of 2026 that's the iPhone 16 and 17 series, though the iPhone 16e is reported to sit outside it. Anything earlier caps at 15W no matter what the charger claims, so paying extra for a 25W pad buys you nothing on an older phone.
A certified Qi2 25W charger. Uncertified pads advertising high wattage frequently don't deliver it.
A wall adapter rated 30W or higher. This is the step almost everyone misses. An old 5W or 12W brick simply doesn't have the headroom, and the system quietly falls back to a slower speed. If your wireless charging feels slow despite new hardware, this is the first thing to check.
Nothing thick or metal in the way. Which brings us to cases.
Can you charge wirelessly through a phone case?
Yes, with two caveats. Both magnetic force and inductive coupling fall off sharply with distance, so total thickness between the two coils is the variable that matters.
For ordinary charging at 15W, general industry guidance is that plastic cases under about 3mm are fine. For peak 25W it's tighter: charger manufacturers advise keeping cases under roughly 2mm, and a dual-layer tough case is thicker than that by definition. Attachment and charging both still work. Maximum speed may not.
Three specific things break wireless charging outright, and none of them is having a case.
Metal anything. A metal plate, a metal ring sticker, or a case with metal detailing over the coil area. Metal interferes with the field directly.
Cards behind the phone. A card tucked between phone and case adds distance and can be damaged by the field. The single most common self-inflicted problem.
A case with no magnets pretending otherwise. Without its own magnet array, the accessory relies on the phone's magnets pulling through an extra layer of plastic: weak attachment, poor alignment, slower charging.
A well-built dual-layer case is thicker than a slim shell, so the magnet array has to be engineered into the design rather than added afterwards. That's what we do: the ring is moulded into the shell so accessories snap on and charging works without removing the case. The label side of this is covered in MagSafe compatible vs Made for MagSafe, and the accessory side in what actually holds on a tough case.
The honest part about speed
Wireless charging is slower and less efficient than a cable, and it always will be, because energy is lost as heat in the transfer. If you need a fast top-up before leaving the house, plug it in.
What wireless is genuinely better at is the passive case: a charger on a desk or bedside table where the phone lives when you're not using it. Under those conditions 25W versus 15W barely matters, because the phone has hours. The speed tier is mostly relevant if you're topping up in short bursts.
So the practical advice for most people: buy a Qi2 charger rather than an old flat Qi pad, because magnetic alignment is the upgrade you'll actually feel every day. Whether it's the 15W or 25W tier matters far less than whether it snaps into place.
The honest limitation
Our cases cost you something at the top charging tier. A dual-layer tough case sits above the roughly 2mm figure charger makers recommend for a full 25W, so on an iPhone 16 or 17 chasing peak speed you may lose some of it. At 15W, and on anything older, you won't notice.
If maximum wireless charging speed matters more to you than drop protection, a slim shell is the better buy and we'd rather say so than have you find out.
FAQ
What's the difference between Qi2 and MagSafe?
MagSafe is Apple's branded system, introduced in 2020. Qi2 is the Wireless Power Consortium's open standard, released in 2023, which adopted the same magnetic alignment approach. Both work with magnetic cases.
Why is my wireless charging slow?
Most often the wall adapter. Reaching 25W requires a USB-C PD adapter of 30W or more; older 5W and 12W bricks force a fallback to slower speeds.
Can you charge wirelessly through a phone case?
Yes, provided the case isn't metal. Plastic cases under roughly 3mm charge fine at 15W, though peak 25W wants something under about 2mm. A case with a built-in magnet array aligns better than one without.
Do I need a Qi2 25W charger?
Only if you have an iPhone 16 or 17. Earlier iPhones cap at 15W regardless of the charger.
Does a thicker case slow wireless charging?
It can at the highest tier. Charging and attachment still work through a dual-layer case, but a full 25W wants under about 2mm of material between the coils.
