I don't know if it's necessarily 100% safe. Theoretically it should be, but I had one of my phones started acting haywire whenever I had it charged into a third party charger. The screen on it would become very erratic and unresponsive whenever it was plugged in. Eventually this became permanent even when I didn't have the phone plugged into that charger specifically. I ended up having to upgrade and get a new phone because it became so unuseable. This was the original Motorola Droid from a few years ago, so perhaps they have designed the phones to be more flexible with chargers these days.