Can I blow up my USB device?

There is a huge variance, then, between normal USB ports rated at 500mA and dedicated charging ports which range all the way up to 3,000mA. This leads to a rather important question: If you take a smartphone which came with a 900mA wall charger, and plug it into a 2,100mA iPad charger, as an example, will it blow up?
In short, no: You can plug any USB device into any USB cable and into any USB port, and nothing will blow up — and in fact, using a more powerful charger should speed up battery charging.
The longer answer is that the age of your device plays an important role, dictating both how fast it can be charged, and whether it can be charged using a wall charger at all. Way back in 2007, the USB Implementers Forum released the Battery Charging Specification, which standardized faster ways of charging USB devices, either by pumping more amps through your PC’s USB ports, or by using a wall charger. Shortly thereafter, USB devices that implemented this spec started to arrive.
If you have a modern USB device — really, almost any smartphone, tablet, or camera — you should be able to plug into a high-amperage USB port and enjoy faster charging. If you have an older device, however, it probably won’t work with USB ports that employ the Battery Charging Specification. It might only work with old school, original (500mA) USB 1.0 and 2.0 PC ports. In some (much older) cases, USB devices can only be charged by computers with specific drivers installed.
There are a few other things to be aware of. While PCs can have two kinds of USB port — standard downstream or charging downstream — OEMs haven’t always labeled them as such. As a result, you might have a device that charges from one port on your laptop, but not from the other. This is a trait of older computers, as there doesn’t seem to be a reason why standard downstream ports would be used, when high-amperage charging ports are available. Numerous vendors now put a small lightning icon above the proper charging port on laptops, and in some cases, those ports can even stay on when the lid is closed.
In a similar vein, some external devices — hard drives and optical drives, most notably — require more power than a USB port can provide, which is why they include a two-USB-port Y-cable, or an external AC power adapter. Otherwise, USB has certainly made charging our gadgets and peripherals much easier than it ever has been. And if the new USB-C connector catches on — and it looks like it will — things will get even simpler, because you’ll never again have to curse after plugging it in the wrong way.