Privacy policy.

Simvora is a free, non-commercial site for learning how systems, classes and algorithms work. It is run by nexus-hash, reachable at support@simvora.dev.

Without an account

You don't need an account to use Simvora. If you don't sign in, we collect no personal data.

• What stays in your browser. Your progress (pages read, steps done, drills solved), your practice code and a few settings (theme, tracks, code language) are kept in your browser's own storage. They never leave your device and we can't see them. Clearing your browser's site data removes them.
• Hosting. Simvora is served by Cloudflare. Like any website, Cloudflare processes your IP address and request details to deliver pages and protect the site from attacks. We don't keep these logs.
• Almost nothing from other sites. Pages load from simvora.dev: our fonts are our own files, and there are no ads or trackers. The one exception is Google's sign-in prompt: if you aren't signed in, the home page loads Google's sign-in script after a few seconds, so Google can offer to sign you in. Google handles that request under its own privacy policy. Ads or trackers may come later; if they do, this policy will say so first.

With an account

Signing in is optional. It saves your progress and practice code to your account so they follow you across devices.

What we store

• If you sign in with Google: your name, your email address and your Google account ID. We don't receive your password, and we don't keep your profile picture or any access to your Google account.
• If you sign in with a passkey: the name you enter, and your passkey's public key and ID, with when it was added and whether it's synced across your devices. Your fingerprint, face or screen lock never leave your device, and we never see the passkey's private key.
• Your progress: which concept pages you've read or know, which designs and practice problems you've finished, steps you've marked by hand, and drills you've ticked, each with when it changed.
• Your practice code: the files you write on low-level design problems, with the open tabs and diagram layout. If two of your devices saved different versions at the same time, we keep the earlier one as well, so you can get it back.
• Your session: a cookie that keeps you signed in for up to 30 days. It's strictly necessary for signing in, so we don't ask for consent to it, and it's the only cookie we set. We don't store your IP address or browser with your session.

What we don't do: no ads, no tracking across sites, no selling or sharing your data, no analytics tied to your account.

Why we store it: to provide your account (the service you ask for), and to keep it secure. To stop abuse, sign-in attempts are counted per IP address; those counters are deleted within a day.

Where it's kept: in a Cloudflare D1 database. Cloudflare processes it for us. If you sign in with Google, Google tells us who you are when you sign in, under Google's own privacy policy.

How long: until you delete your account. Expired sessions are removed daily. Cloudflare's database backups roll off on their own within 7 days.

Your choices and rights

On your account page you can:

• Download your data: one file with everything your account holds.
• Delete your account: everything is deleted at once, and it can't be undone.

You can also write to support@simvora.dev to ask what we hold about you, to correct it, or to have it deleted. Under the EU and UK GDPR and India's Digital Personal Data Protection Act you have these rights, and you can complain to your data protection authority. For India, support@simvora.dev is also the contact for grievances.

Children

Accounts are for people aged 15 and over. Everything else on Simvora is open to everyone, without an account.

Changes

This policy may change, and the owner can change it at any time. The new version will be posted here with a new date. If a change affects what we do with account data, we'll say so on the site before it takes effect.