It works okay on my berber carpet. My chair had already made indents into the carpet so with the mat on top my chair tends to roll to where the indents were.
In just a week my chair has formed near permanent dents in the so-called carpet mat. The mat is clearly substandard and cannot be used on anything except a hard floor. Very disappointed.
Great mat for the price. I was using a heavier desk chair and it did make large "divits" that were a little difficult to roll out of. I switched to a little lighter chair and it's been better. Definitely better than not having one but if I do wish I had invested in a little thicker mat.