There's a great product in Canada called "Goo Gone" you can buy it at hardware or department stores in the cleaner section. I removed really old decals off windows and doors successfully with it.
When I get a picture fram with a price sticker on the glass I use plain old cooking oil on paper towel and rub the area of sticky residue. Then when it is off I wash it with soap and water and dry to see if it is all gone for sure. Works on anything that is not going to be marred with oil stain. I have used it on some wood frames that had sticker on the back, lawn furniture, cookware, dinnerware, flatwear also. Not recommended for clothing or anything fabric.
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