Privacy
Last updated 2 October 2026.
What we collect
- Usage analytics through Google Analytics (via Firebase): pages viewed, buttons clicked, approximate country, device and browser. Used to see which pages and challenges help people.
- Session recordings through Microsoft Clarity: mouse movement, clicks and scrolling on our pages, so we can find where the product is confusing. Form fields are masked.
- Error reports through Sentry when the simulator crashes, so we can fix it.
- Your email address, only if you sign up for the weekly problem, stored on Cloudflare together with the page you signed up from and the campaign that brought you.
- Challenge progress and your playground design, stored only in your own browser.
What we don't do
- We don't sell or share your email address.
- We don't require an account for anything.
- We only email you about System Design Sim, and every email has an unsubscribe link.
Removing your data
- Email hello@systemdesignsim.com and we will delete your email address and any signup data within 30 days.
- Clearing your browser's site data removes your saved challenge progress and designs.