Privacy by default means the protective behaviour happens without configuration. Here is how to tell default privacy from a checkbox, and what it changes in practice.
Three private surfaces. Same zero-knowledge architecture.
In European data-protection language, it is a legal principle: only the personal data necessary for a specific purpose should be processed, by default. In engineering terms, it means the safe path must also be the easy path.
There is no "privacy plan". The free 1 GB account uses exactly the same architecture as the largest business account.
Three private surfaces. Same zero-knowledge architecture.