Security and your data

Where your model goes when you analyse it, how signing in works, what we keep and for how long.

Where it runs

Our servers are hosted by Hetzner Online GmbH in Nuremberg, Germany. Backups are encrypted and stored off our server, with Cloudflare R2.

Where your model goes

  • Analysed in the browser — it stays on your computer. The solver runs inside the page, on your machine. A model you open, build or import and analyse only in the browser is never sent to our servers.
  • Saved to a cloud project — it is stored on our servers, with any files you attach to it, so you and the people you share the project with can open it. It stays until you delete it or your account.
  • Analysed on the cloud engine (Pro and Team) — it is sent to our server for the run. The job and its results are held in memory only, never written to disk, and forgotten as soon as the app has collected them, or 15 minutes after the run at the latest.
  • Edited with the AI copilot — it is sent with your message, through our server, to an AI model provider. See below.

Signing in

  • Three ways in: Google, a one-time code sent to your email (valid for 15 minutes), or a password (at least 8 characters). Passwords are stored salted and hashed, never as text.
  • After five failed attempts the account is locked for a while.
  • In the browser your session is held in two HttpOnly, Secure cookies that page scripts cannot read: one for 24 hours, sent only to our API, and one for 30 days that can only renew it.
  • One browser session per account: signing in on another browser signs the first one out. Your account page lists your sessions — including the desktop app and any AI assistant you connected — and can end any of them, or all at once.
  • The desktop app signs in through your web browser and keeps its token in your operating system’s credential store.

In transit

Every connection to structlib.com and app.structlib.com is HTTPS; browsers are told to use nothing else (HSTS). Traffic passes through Cloudflare on its way to our server.

The AI copilot

Each copilot turn sends your message and the open model through our server to OpenRouter, which passes it to the AI model provider that answers — currently Anthropic or OpenAI. Conversations are kept so that you can return to them: a conversation you delete disappears at once and is erased 90 days later, and the text of any message is cleared 12 months after it was written. The copilot never produces results — the analysis engine computes every number.

How long we keep things

  • Your account and saved models: until you delete them. Delete your account from the account page (Delete My Account), or email us, and your account and saved models are deleted within 30 days.
  • Backups roll over within 90 days, so a deleted item is gone from them too by then.
  • Cloud analysis results: minutes, in memory only (above).
  • Copilot conversations: as above.

The full list of what we collect, why, and who processes it is in the Privacy Policy.

Report a problem

If you think you have found a security issue, email [email protected]. Please give us a chance to fix it before telling anyone else.