It's disinflationary. Everyone running a node has a copy of the blockchain. Its distribution schedule is fixed. Every 4 years that distribution amount is cut in half in an event known as the halving. Over 92% of all bitcoin has been mined. Do the math. There isn't a hard cap coded into the software, but the distribution halving brings issuance to effectively zero around 2140, which is about the same as a hard cap.