DLL and COM Interface Backward Compatibility — A Decision Table for Which Changes Break Callers (archived 2026-07-27)

Which changes to a DLL or COM component actually break their callers? We lay out the three layers of compatibility — binary, source, and behavioral — a decision table organized by kind of change, the iron rule that COM interfaces never change, and a practical guide to running semver. Archived version of https://comcomponent.com/en/blog/dll-com-interface-backward-compatibility/, as published on 2026-07-27. The live article is maintained and may change after this date. First published 2026-07-17.