Stickers are easy to remove from a hard, non-porous material like a mirror. Putting chemicals on the sticker in an effort to remove them will not damage the surface. You can remove a sticker from a mirror without damaging it if you use some special tools. Never use a knife or sharp, pointed object on a mirror or else you may scratch it. Once you melt the sticker's adhesive, you should be able to easily take it off the mirror without damaging it.
Things You'll Need
Mineral oil or Goo-Gone
Apply some mineral oil or a product specially formulated to remove stickers, such as Goo-Gone, to the sticker. Pour it over the sticker and wait half an hour for the sticker to become fully saturated. The Goo-Gone or mineral oil will melt the adhesive and make the removal process easier.
Insert a new, flat razor blade into a scraper holder, which you can find at a hardware store. The scraper prevents the razor from scratching the mirror with its sharp edges, and also protects your fingers.
Scrape the sticker off with the razor, being careful not to press down too hard.
Spray the mirror with glass cleaner and wipe away the rest of the sticker residue with paper towels.
Using a razor without a scraper holder may cause injury or damage the mirror.