You’ll hear both sides of the answer on the internet. In fact, it’s hard to tell sometimes what the right thing to do is with so many conflicting voices.
Generally, it’s a best practice to avoid using Windex on quartz countertops. It’s probably safe to use occasionally, but the better option is to buy a stone cleaner recommended by your quartz countertop manufacturer. The reason people like Windex is that it’s easy to use and can help get rid of gunk or buildup on your countertops. However, those who warn against using it cite that the alkaline pH levels of Windex are potentially damaging to the resins in the countertop. Because of this, it’s best to stick to mild cleaners and routine maintenance of your countertops.
In fact, one of the best cleaners is simply a little dish soap and water. Wipe up spills and messes as soon as you can, followed by wiping it all down with sudsy water, and then wipe it dry. If a more heavy-duty cleaning is needed in some area of your workspace, try using isopropyl alcohol (or rubbing alcohol) to address the problem.