What data you collect, how you use it, and what the law requires
If your product touches personal information — and virtually every software product does — data privacy law applies to you. The question isn't whether you have compliance obligations; it's which ones, in how many jurisdictions, and how strict they are. The US has no single federal privacy law. Instead, a patchwork of sector-specific federal laws and a growing number of state comprehensive privacy laws govern how companies collect, use, and protect personal data.
The most practically significant laws depend on who your users are and where they live. GDPR applies if you have users in the EU — regardless of where your company is located. CCPA/CPRA applies to California residents. A growing number of states now have their own comprehensive privacy laws that impose similar obligations with varying thresholds. HIPAA applies if you touch health data. COPPA applies if you knowingly collect data from children under 13. Getting this right requires understanding which laws apply to your specific situation before you design your data practices — retrofitting compliance is significantly more expensive than building it in.