The major difference between a window cling and a decal is that clings do not include any adhesive material, unlike decals. While they can both stick on glass windows, only clings can be repositioned. Nonetheless, decals are a lot more stronger and can last for a very long time until you feel like removing them. In terms of removal, wall decals are a lot more complicated. You’ll need a razor blade, soap, and water to remove the remaining adhesive on the surface whereas window clings can simply be peeled off from the window without needing any cleanup.