WHQL (Windows Hardware Quality Labs) is the Microsoft team that provides the logo program for hardware compatibility certification. Hardware that passes WHQL testing has the right to display the "Designed for Windows" logo. Microsoft has found that when users complain about the stability of the Windows kernel, in most cases, major quality problems are caused by third party hardware or software. WHQL’s standard testing procedure helps minimize this kind of problem by testing a vendor’s hardware or software before it’s released to the market. This makes it easier for consumers, since they only need to look for products that display the “Designed for Windows” logo.		  
  The major goal of the WHQL logo program is to benefit users of hardware and software that rely on the Windows operating system. WHQL updates the logo requirements when new versions of Windows are launched. The requirements give design guidelines about how to implement hardware and software that uses Windows. Moxa proves their commitment to providing quality products to their customers by providing WHQL certified products.

Microsoft also provides WER (Windows Error Reporting) and DDC (Driver Distribution Center) for WHQL drivers to improve driver quality. If a user gets a BSOD (Blue Screen of Death), the user can send the crash data to WHQL. WHQL will analyze the crash data to see if the BSOD is caused by the Windows kernel or a third party driver, and then record the result in their WER database. Hardware vendors can log into WHQL to view the analysis of WER data. If a bug is reported, vendors are obligated to determine what the problem is, and then update the driver into the DDC. The next time the user’s system connects to “Windows Update,” the new driver will appear on an update list, and the user can download the driver to solve their BSOD problem.
 
  Before certification, WHQL provides WLK (Windows Logo Kits) to hardware vendors for testing. The vendors must use this kit to test the products by themselves, and submit the test log to WHQL for review. When designing products, vendors must follow all WHQL logo program requirements and solve all testing problems before submitting the test log. If the result is ok, WHQL will give the vendor a driver signature, which the vendor includes in the driver package. When users install the logo-certified driver, Windows will check the signature to see whether or not the driver has passed WHQL testing. Without the driver signature, Windows will show a warning message. This message will slow down the installation procedure, which is one of the main reasons most customers request WHQL drivers.
 
 

WHQL testing helps to ensure the quality of hardware and software products. For hardware vendors, developing qualified drivers is not easy because of the complicated WDM (Windows Driver Model) Windows driver architecture. Driver BSOD is often caused by insufficient testing expertise. According to expert analysis, most BSOD cases are caused by installation and power management problems. During WHQL testing, drivers are installed and uninstalled many times and in different orders for stress testing. The testing PC is also put into hibernate and sleep mode many times to check the driver's power management function.

WHQL testing will also test a device’s basic function. For example, it will test serial communication for USB serial adaptors, power management, and USB compatibility.