They can often be interchanged. There are however some patterns emerging in their usage. Cyber diplomacy is used more to refer to diplomatic activities related to cyber security issues. There is more confusion about digital diplomacy being used to implement digital foreign policy (new topics in diplomatic agenda) and the use of new tools in diplomatic practice like social media, websites and online meeting platforms.
It is possible to avoid confusion in the current, transitory phase of terminology settling.
- The evolving geopolitical ENVIRONMENT for diplomacy: impact of digital technology on sovereignty distribution of power, and global interdependence among other issues.
- The emergence of new TOPICS in diplomatic agenda: cybersecurity. internet governance, e-commerce, online human rights, and more than 50 other policy topics.
- Use of new TOOLS in diplomatic practice: social media, AI, big data, online meetings, virtual and augmented reality.
You can read more on terminological confusion and other aspects of digital diplomacy.