A swear jar (also known as a swear box, swearing jar, cuss jar, or cuss bank) is a device to help discourage people from swearing. Every time someone utters a swear word, others who witness it collect a "fine", by insisting that the offender put some money into the box. The container may be made of glass, porcelain, or metal, and may have a lid with a slot. From time to time, the accumulated money may be used for some agreed-upon purpose, or contributed to charity.
A swear jar might not be a physical object; instead, a notional swear jar is referred to by people to indicate someone's use of bad language has been noted.
Most swear jars are homemade, however tins and boxes specifically designed for the purpose are marketed commercially, some of which have a "scale of charges" printed on them. Various materials are used to produce them. Earlier designs were commonly porcelain. Modern versions, often glass, are available online via eBay, other shopping websites, and even sites dedicated to selling only swear jars.