Windows Hardware Quality Labs (WHQL) is a Microsoft procedure for certifying that the hardware for peripherals and other components is compatible (works as expected) with Microsoft Windows operating systems. WHQL provides test kits to third-party developers so that they can test their product's compatibility. Products that are submitted to and meet the tests at Microsoft are allowed to display the Microsoft Windows logo on their marketing materials and are included in Microsoft's Hardware Compatibility List (HCL).
A hardware developer downloads a WHQL test kit for a specific product from Microsoft's Web site. The test kit includes a test tool, test procedures, and errata and is used throughout the development process of the hardware component. The errata shows which errors encountered during testing are not considered a failure of the component and are overlooked by WHQL. When the component is finished, the latest WHQL test kit is downloaded and used to test the final product. If the component passes, the developer submits his test to WHQL.
After WHQL receives the test submission, the developer is notified by e-mail within three days that the submission was received. WHQL processes the submission, which can take up to 30 days. WHQL then sends the developer a report via e-mail. If the component passed, the developer receives a signed Logo License Agreement with a logo kit containing the camera-ready logo artwork, an inclusion of the hardware component in Microsoft's Hardware Compatibility List (HCL), and a distribution of the hardware driver, if needed, on Microsoft's Windows Driver Library. If the component didn't pass, the developer must make the necessary changes to the component and retest.