Bulgaria and Romania have been fully integrated into the Schengen Area, as of 1 Jan 2025.
The free-travel area now includes all EU states except Cyprus, which is in the process of joining, and Ireland, whose membership is complicated by its Common Trade Area with former EU-member the United Kingdom. Also members are four non-EU states: Iceland, Switzerland, Norway and Liechtenstein.
There are also four small countries that are not officially in Schengen but effectively have open borders with a Schengen state or two: San Marino, Andorra, Monaco, and the Vatican.