APIs can undergo changes that are classified as breaking or non-breaking, with breaking changes potentially disrupting client integrations. While non-breaking changes, often referred to as additive changes, are generally safe, the definition can vary based on client implementation. Common breaking changes include adding stricter server-side validation, introducing new required fields, removing existing response body fields or headers, altering permissions, eliminating an authentication type, removing query parameters, changing field types, removing enum options, significantly altering behavior, or modifying return types and response codes. Exceptions exist, such as more informative error code changes, but success code alterations often lead to issues. These nuances highlight the complexity of maintaining API compatibility and the importance of careful change management.