What do we call a document that gives special rights to a town?

The story behind the answer

In medieval Europe, towns gained privileges through a formal document issued by a king or lord that granted rights such as self-government, market holding, toll exemptions, and the election of local officials. This legal instrument distinguished a town from the surrounding feudal countryside. By contrast, a deed transfers property, an ordinance is a rule or bylaw, and a patent grants exclusive rights to an invention—none of which conferred broad civic liberties.

These documents powered urban growth. Under frameworks like the Lübeck Law or English borough charters, merchants and guilds thrived, courts became local, and taxes were negotiated collectively. The saying “city air makes you free” captured a key effect: serfs who settled in chartered towns could often gain personal freedom after a set period.