Compliance means products that are called USBproducts are really built to match the description in the USB specification. This is important to consumers because if all products are in compliance with the specification they would by definition work together perfectly. Compliance testing exists to help manufacturers measure how well their products match the specification. There are many ways to make sure products work together and many ways to see if they match the specification, but compliance testing is one of the most useful. Conscientious manufacturers do a great deal of testing on their own and use compliance test programs like the one sponsored by the USB-IF organization. Click here to learn more about compliance testing.