Legal

1. Acceptance

By accessing or using ButterflyForge, you agree to these Terms of Service. If you do not agree, do not use the service.

2. Description of Service

ButterflyForge provides Monte Carlo simulation tools for financial scenario modelling. The simulations are based on aggregated, publicly available historical market data and statistical models. The free version offers basic simulations. The Personal Edition provides additional features and is available as a one-time purchase.

3. Not Financial Advice

ButterflyForge does not provide financial advice of any kind. It is not a financial advisor, broker, fiduciary, or licensed professional. The service does not recommend investments, strategies, or courses of action.

All simulation results are hypothetical, generated by computational models using historical data and statistical assumptions. They are not predictions, forecasts, or guarantees of future performance. Past performance does not guarantee future results. Markets are inherently unpredictable and any model — no matter how sophisticated — is a simplification of reality.

The tool exists to help you build intuition, experiment with scenarios, and explore "what if" questions. It is your responsibility to do your own research, perform your own due diligence, and seek qualified professional advice before making any financial, investment, or retirement decisions. Do not rely on simulation results as the basis for financial decisions.

4. Data Sources

Simulation models are calibrated using publicly available, long-run market statistics. ButterflyForge does not provide, redistribute, or resell market data.

5. No Warranty

The service is provided "as is" and "as available" without warranty of any kind, express or implied, including but not limited to warranties of merchantability, fitness for a particular purpose, or accuracy of results. We do not guarantee that the service will be uninterrupted, error-free, or that simulation results are accurate, complete, or reliable.

6. Limitation of Liability

To the maximum extent permitted by applicable law, the creators of ButterflyForge shall not be liable for any direct, indirect, incidental, special, consequential, or punitive damages arising from or related to your use of the service, your reliance on simulation results, or any decisions made based on information provided by the service. This includes, without limitation, financial losses, investment losses, or missed opportunities.

7. Accounts & Authentication

Access to the Personal Edition requires an account. Authentication is handled via passwordless magic links sent to your email address. You are responsible for maintaining access to your email account. We do not store passwords.

8. Personal Edition & Purchases

The Personal Edition is licensed for personal, non-commercial use only. It is intended for individuals managing their own financial planning. Using the Personal Edition to provide services to third parties — including but not limited to financial advising, consulting, or portfolio management for clients — is not permitted under this license. If you are a financial professional interested in using ButterflyForge with clients, please contact us about our professional plans.

The Personal Edition is sold as a one-time purchase granting access to the features available at the time of purchase. Purchases are processed by Paddle, which acts as the Merchant of Record. We do not process or store payment details directly.

Refunds: If you are not satisfied with the Personal Edition, you may request a full refund within 14 days of purchase, no questions asked. To request a refund, use the refund link in your Paddle purchase receipt. Refunds are processed by Paddle and typically arrive within 5–10 business days. After 14 days, all sales are final.

The one-time purchase grants access to the Personal Edition for as long as the service remains operational. We do not guarantee that the service will be available indefinitely. ButterflyForge is a personal project and may be modified, suspended, or discontinued at any time without prior notice. In such case, no refunds or compensation will be provided, except as required by applicable law.

New features, modules, or capabilities may be added to the service over time. Such additions may be included in the existing Personal Edition or may be offered under separate terms, at our sole discretion. The one-time purchase does not constitute an entitlement to all future features or updates.

9. Fair Use & Rate Limiting

ButterflyForge applies rate limiting to simulation requests to ensure a stable and responsive experience for all users. If you exceed the rate limit, your requests will be temporarily paused and you will be notified with an estimated wait time. Normal interactive use is well within these limits.

Sustained high-volume usage — whether manual or automated — that degrades the service for others may result in temporary or permanent restriction of access. We reserve the right to adjust rate limits at any time without prior notice.

Automated requests — including scraping, bots, scripts, and programmatic access — are not permitted without prior agreement and may result in immediate account cancellation without refund. If you are interested in API access for integration, research, batch processing, or commercial use, please contact us to discuss options.

10. Sharing & Attribution

You may share screenshots or exports of your simulation results, provided that:

• You have full permission from every person whose personal data (name, age, financial details) is visible in the scenario.
• You attribute the results to ButterflyForge (e.g. "Simulated with ButterflyForge" or a link to butterflyforge.app).
• You include a clear disclaimer that the results are simulations, not predictions or financial advice.

11. Modifications to Terms

We reserve the right to modify these terms at any time. Material changes will be communicated through the service where practicable. If you do not agree with updated terms, you may stop using the service. Continued use of the service after changes have been communicated constitutes acceptance of the updated terms.

What we collect

ButterflyForge is designed to be privacy-friendly. We collect minimal data:

• Account & authentication: When you sign up, we store your email address and a session token. We use passwordless magic link authentication — no passwords are stored. Sessions expire after 7 days. Your account also stores your display currency preference, notification preferences, and optional default people (name, birth year, retirement age) for pre-filling simulations.
• Launch notifications: If you sign up for launch notifications, we store your email address with a confirmation token. This is a GDPR-compliant double opt-in process: we send a confirmation email, and your address is only retained if you click the confirmation link. Unconfirmed addresses are automatically deleted after 7 days. We store the IP address of the signup request solely for rate-limiting purposes. You can unsubscribe at any time via the link in the confirmation email. We will send exactly one notification when the Personal Edition launches, then delete all launch notification email addresses.
• Analytics: We use self-hosted Umami at analytics.butterflyforge.app for website analytics. It is cookieless, does not collect personal data or IP addresses, and all data is stored on our own server. No analytics data is shared with third parties.
• Error tracking: We use self-hosted GlitchTip at errors.butterflyforge.app for error monitoring. When an application error occurs, technical information about the error (stack trace, browser type, page URL) may be captured. No personal or financial data from your simulations is included.
• Payments: Payment processing for the Personal Edition is handled by Paddle, which acts as the Merchant of Record. We store a Paddle customer ID and license key on our server. Paddle processes your payment details directly — we never see or store your credit card or bank information. Paddle's privacy policy applies to all payment transactions.
• Simulation data: Your simulation parameters are sent to our API for processing and are not stored after the response is returned. If you explicitly save a scenario, your parameters are stored on our server so you can revisit or share them. Saved scenarios can be deleted by you at any time. We do not analyse your financial scenarios or share them with third parties.

Email

All emails — transactional (magic login links, launch notification confirmations) and occasional newsletters or update reminders (if you opt in) — are sent via Resend. Resend processes your email address solely for the purpose of delivering the email. You can opt out of newsletters and update reminders at any time in your account settings. See Resend's privacy policy for how they handle data in transit.

Cookies

ButterflyForge uses only essential, functional cookies:

• Session token — signed cookie to keep you logged in (expires after 7 days)
• Disclaimer acknowledged — remembers that you accepted the simulation disclaimer
• Tour completed — remembers that you finished the guided tour

No advertising cookies, no tracking cookies. Our analytics solution (Umami) is fully cookieless. Cloudflare may set functional cookies (e.g. __cf_bm) for bot detection — these are not used for tracking or advertising. During checkout, Paddle may set its own cookies within its checkout overlay — see their respective privacy policies for details.

Infrastructure & third parties

All traffic to ButterflyForge is routed through Cloudflare, which acts as a reverse proxy and provides DDoS protection, TLS termination, and content delivery. Cloudflare may process your IP address and request metadata (headers, URL, timing) as part of its normal operation. Cloudflare's own cookies or headers (e.g. __cf_bm) may be set for bot detection. See Cloudflare's privacy policy for details on how they handle this data.

We share data with the following third parties, and no others:

• Cloudflare — reverse proxy, DDoS protection, and content delivery (processes IP addresses and request metadata)
• Paddle — payment processing (Merchant of Record)
• Resend — transactional email delivery

Data controller

The data controller responsible for processing your personal data is Robert Jung, as identified in the Impressum below. For any privacy-related questions or requests, contact us at the email address listed in the Impressum.

Legal basis for processing

We process personal data under the following legal bases (GDPR Art. 6):

• Contract performance (Art. 6(1)(b)) — Account creation, authentication, session management, license key storage, and simulation processing. These are necessary to provide the service you signed up for.
• Legitimate interest (Art. 6(1)(f)) — Error tracking (maintaining service reliability), analytics (understanding usage to improve the service), rate-limiting (preventing abuse), and infrastructure services (Cloudflare for security and performance). In each case, our interest does not override your rights, as we minimise the data collected and use privacy-friendly, self-hosted tools where possible.
• Consent (Art. 6(1)(a)) — Newsletter and yearly reminder emails, launch notification waitlist signup. You can withdraw consent at any time in your account settings or via the unsubscribe link in any email.

Data location & transfers

All ButterflyForge servers — including the application, database, analytics, and error tracking — are hosted on Hetzner servers located in Germany. Your data is stored and processed within the European Union.

Some third-party services may process data outside the EEA as part of their normal operation:

• Cloudflare may route traffic through global edge nodes, including outside the EEA. Cloudflare participates in the EU–U.S. Data Privacy Framework.
• Paddle processes payments and may transfer data internationally as part of payment processing. Paddle operates under Standard Contractual Clauses (SCCs) where applicable.
• Resend delivers emails and may process your email address on servers outside the EEA. See Resend's privacy policy for their transfer safeguards.

Data retention

• Account data: Retained for as long as your account exists. When you delete your account, all associated data (email, preferences, saved scenarios, default people) is permanently deleted. Note that deleting your account means you lose access to the Personal Edition — the license is tied to your account and cannot be recovered after deletion.
• Session tokens: Expire and are deleted after 7 days.
• Simulation data: Not stored after the response is returned, unless you explicitly save a scenario. Saved scenarios are retained until you delete them or your account.
• Launch notification waitlist: Unconfirmed signups are deleted after 7 days. Confirmed addresses are retained until we send a single launch notification, then immediately deleted.
• Newsletter & reminder emails: If you opt in, your email preference is stored as part of your account. Emails are sent strictly for the purpose you consented to (newsletter updates or yearly planning reminders). You can revoke consent at any time in your account settings, and we will stop sending these emails immediately.
• Payment records: Paddle customer ID and license key are retained as long as your account exists, for license verification purposes.
• Database backups: Deleted data may persist in encrypted database backups for up to 30 days, after which backups are rotated and the data is permanently removed.

Your rights

Under GDPR, you have the following rights regarding your personal data:

• Access (Art. 15) — Request a copy of the personal data we hold about you.
• Rectification (Art. 16) — Request correction of inaccurate data.
• Erasure (Art. 17) — Request deletion of your data. You can delete your account and saved scenarios yourself at any time. For other data requests, contact us.
• Restriction (Art. 18) — Request that we limit processing of your data in certain circumstances.
• Data portability (Art. 20) — Request your data in a machine-readable format.
• Objection (Art. 21) — Object to processing based on legitimate interest.
• Withdraw consent — Where processing is based on consent (newsletters, waitlist), you can withdraw at any time without affecting the lawfulness of prior processing.

To exercise any of these rights, contact us at the email address listed in the Impressum below. We will respond within 30 days.

Supervisory authority

If you believe that our processing of your personal data violates data protection law, you have the right to lodge a complaint with a supervisory authority. The competent authority for ButterflyForge is:

Der Hamburgische Beauftragte für Datenschutz und Informationsfreiheit (HmbBfDI)
https://datenschutz-hamburg.de