Plastic bags are bags made primarily from plastic (commonly used plastics include polypropylene, polyester, nylon, etc.) and are essential items in people's daily lives, often used to hold other items. Due to its advantages of low cost, extremely light weight, large capacity, and easy storage, plastic bags are widely used. However, due to the long degradation cycle and difficult handling of plastic bags, their production and use have been banned by some countries.

Since June 1, 2008, China has implemented a plastic restriction order: "A system of paid use of plastic shopping bags shall be implemented in all supermarkets, shopping malls, markets and other commodity retail places. Plastic shopping bags shall not be provided for free, and the production, sale and use of plastic shopping bags with a thickness less than 0.025 millimeters shall be prohibited nationwide.

In March 2018, the Panamanian government announced that they had decided to ban the use of disposable plastic bags in stores in order to reduce the amount of marine litter in the Pacific and Caribbean regions.

The commonly used food plastic bags are mostly made of polyethylene film, which is non-toxic and can be used to hold food. There is also a type of film made of polyvinyl chloride, which itself is non-toxic, but the additives added to the film are often harmful to the human body and have a certain degree of toxicity. So these types of films and plastic bags made from them are not suitable for holding food. To distinguish between polyvinyl chloride plastic bags and polyethylene plastic bags, the following simple method can be used for identification.