Privacy Policy
Overview
System Design Simulator is a free, browser-based learning platform. It is intentionally built to collect as little data about you as possible. This page explains exactly what we store and why.
What we collect
The app stores a small amount of state in your browser's localStorage so that the UI remembers your preferences between visits. Specifically:
hld.mode— which tab you last had open (HLD Designs / System Internals / DSA).hld.selectedDesignId— which system design you last opened.hld.aboutSeen— whether you have dismissed the welcome dialog.hld.customDesigns— any custom designs you generated (feature currently disabled in the public demo, kept for forward compatibility).
This data stays on your device. The application does not send it anywhere.
What we do not collect
- We do not use analytics, tracking pixels, or third-party trackers.
- We do not use cookies for tracking. The app uses browser
localStorageonly for the preferences listed above. - We do not ask for or store your name, email, IP address, or any other personal information.
- We do not require sign-up or login of any kind.
Hosting
The site is hosted on Vercel. Vercel may log standard server-access metadata (IP address, user agent, request time) in line with their privacy policy. We do not access, retain, or analyse those logs.
Third-party links
Some pages link to external resources (GitHub, LeetCode, Wikipedia, etc.). Clicking those links takes you to sites with their own privacy policies, which we do not control.
Future advertising
If advertising is introduced in the future, it will be disclosed here and we will update this policy with the specific ad provider's data-handling terms. Advertising is not active today.
Children
This site is an educational tool intended for a general technical audience. It is not directed at children under 13 and we do not knowingly collect any data from them.
Your rights
Because the site holds no personal data server-side, there is nothing for us to export or delete on your behalf. You can clear the local preferences at any time by clearing your browser's site data for systemdesignsimulator.org.
Contact
If you have a question about this policy, reach out via the contact page.