Perdura logo Perdura
Pricing Open App

Terms of Service

Last updated: October 13, 2026

These Terms of Service ("Terms") govern your use of Perdura ("the Service"), a chess opening preparation tool operated by Perdura ("we", "us", "our"). By accessing or using the Service, you agree to be bound by these Terms.

1. Accounts

To access certain features, you must create an account by providing a valid email address. You are responsible for maintaining the security of your account.

Each account is for a single individual. You may not share your account credentials or allow others to access your account. Accounts found to be shared may be suspended or terminated without refund.

We may limit the number of concurrent sessions per account to enforce this policy.

2. Subscriptions and Payments

Perdura offers free and paid tiers. Paid subscriptions are billed through Stripe. By subscribing, you authorize us to charge your payment method on a recurring basis until you cancel.

  • Pro subscriptions renew automatically (monthly or yearly). You may cancel at any time from your Profile (Profile, Subscription, "Cancel subscription"); access continues until the end of the current billing period, or of the free trial, and you are not charged again.
  • Supporter (Lifetime) is a one-time payment granting permanent access to Pro features for the lifetime of the Service. "Lifetime" means for as long as Perdura is commercially operated — it does not guarantee perpetual availability if the Service is discontinued.

All prices are in Euros (EUR) and include applicable taxes unless stated otherwise.

3. Free Tier Limits

Free accounts are subject to daily search limits and reduced engine analysis depth. These limits may change at our discretion. Attempting to circumvent limits (e.g., creating multiple accounts, automated access) is prohibited.

4. Acceptable Use

You agree not to:

  • Share, resell, or sublicense your account access
  • Scrape, crawl, or programmatically extract data from the Service beyond normal API usage
  • Reverse engineer, decompile, or attempt to extract the source code of the Service
  • Use the Service for any unlawful purpose
  • Interfere with or disrupt the Service's infrastructure
  • Create multiple free accounts to circumvent usage limits

5. Intellectual Property

The Service, including its design, code, and branding, is owned by Perdura. Chess game data sourced from public databases (TWIC, FIDE, Lichess, etc.) remains subject to their respective licenses and terms.

The in-browser analysis engine is Stockfish, free software under the GNU General Public License v3. Its source code is available at github.com/nmrugg/stockfish.js. Nothing in these Terms, including Section 4, limits your rights to that engine under its license.

Games from Lichess broadcasts (live and the monthly broadcast database) are licensed under CC BY-SA 4.0. PGN exports mark each of those games with Source and License tags; if you share them, credit Lichess and keep the same license. Nothing in these Terms, including Section 4, limits your rights to those games under that license.

Your analysis, preparation notes, and other content you create using the Service remain yours.

6. Data and Privacy

We collect your email address for authentication and may collect anonymized usage data to improve the Service. We do not sell your personal data to third parties.

Payment information is processed by Stripe and is never stored on our servers. For details, see our Privacy Policy.

7. Refunds

Pro subscriptions may be cancelled at any time. We do not provide prorated refunds for partial billing periods.

Supporter (Lifetime) purchases are generally non-refundable. If you are unsatisfied within 14 days of purchase and have not extensively used the Service, contact us to discuss a refund.

8. Termination

We reserve the right to suspend or terminate accounts that violate these Terms, including but not limited to account sharing, abuse, or circumvention of limits. Terminated accounts forfeit access to paid features without refund.

You may delete your account at any time by contacting us. Upon deletion, your personal data will be removed within 30 days.

9. Disclaimer of Warranties

The Service is provided "as is" without warranties of any kind, express or implied. We do not guarantee uninterrupted availability, accuracy of game data, or suitability for any particular purpose. Engine analysis is provided for study purposes and may contain errors.

10. Limitation of Liability

To the maximum extent permitted by law, Perdura shall not be liable for any indirect, incidental, or consequential damages arising from your use of the Service. Our total liability shall not exceed the amount you have paid us in the 12 months preceding the claim.

11. Changes to These Terms

We may update these Terms from time to time. Material changes will be communicated via email or a notice within the Service. Continued use after changes constitutes acceptance.

12. Governing Law

These Terms are governed by the laws of the European Union and the jurisdiction in which the operating entity is registered. The specific governing jurisdiction will be updated here once the legal entity is established.

13. Contact

Questions about these Terms? Contact us at hello@perdura.app.

Perdura — Chess Opening Preparation