Yes, GA4 is free to use, but you may need to pay for certain advanced features or integrations, like BigQuery export, if you exceed the free monthly quota.
GA4 is the latest version of Google Analytics that focus on App+Web properties and allows to track user interactions across multiple devices and platforms. It also provide new features like enhanced measurement, cross-device reporting, and improved data accuracy.
It is important to note that some features of GA4 are only available to those with a Google Analytics 360 subscription or a Google Workspace plan.