To safely view an eclipse, it is important to use proper eye protection. Eclipse glasses are specifically designed for this purpose and use lenses made of black polymer, which are about 100,000 times darker than ordinary sunglasses and block nearly all visible light as well as all infrared and ultraviolet light. To ensure that eclipse glasses are safe, they should meet the ISO 12312-2 international safety standard. Filters that are ISO 12312-2 compliant not only reduce visible sunlight to safe and comfortable levels but also block all but a tiny fraction of solar UV and IR radiation. It is important to avoid using ordinary sunglasses, neutral density or polarizing filters made for camera lenses, or multiple pairs of sunglasses. When purchasing eclipse glasses, it is recommended to buy from reputable sellers featured on the American Astronomical Societys list of approved vendors or from others that have been approved by the ISO. It is also important to check the safety standards of any glasses you plan to use to view a solar eclipse, and to avoid buying cheap or counterfeit glasses from places like Amazon or eBay.