The deal, in plain words.

Cycle0 is published by Steffen Meyer, Eibenweg 1, 4500 Solothurn, Switzerland. Reach out anytime at hello@cycle0.app. Full legal details are available on the imprint page.

These terms apply to the Cycle0 app across all supported platforms and to this website. Installing or using Cycle0 indicates acceptance of these terms. If you do not agree, please do not install or use the app. Store refunds are handled directly by the respective platform under Section 4.

Cycle0 is a private diary for your cycle. It stores the data you enter and calculates basic metrics—such as averages, cycle lengths, and estimated future dates once sufficient history exists.

It is not a medical device and makes no medical claims. It does not diagnose, screen for, or treat any condition, nor does it determine fertility, pregnancy, or general health status. Predictions are estimates based on your past entries and can be inaccurate, particularly when cycles vary. Cycle0 is not a contraceptive and must not be used to avoid or achieve pregnancy.

Health information linked within the app leads to external resources (such as the NHS, WHO, and NICHD) that are neither written nor controlled by Cycle0. If you have health concerns, consult a qualified clinician.

Cycle0 is purchased through the Apple App Store or Google Play. These platforms handle processing payments, setting local pricing and currencies, issuing receipts, and managing refunds under their respective terms. Cycle0 does not receive or store payment details and cannot process refunds directly. A purchase grants access on supported platforms tied to your store account; it is a one-time purchase, not a subscription.

You receive a personal, non-exclusive, non-transferable licence to use Cycle0 on devices authorized by your store account.

You may not resell, rent, redistribute, or publish modified versions of the app. Reverse engineering or attempting to bypass technical protections is prohibited, except where explicitly permitted by applicable law. All rights, title, and interest in Cycle0—including its name, brand assets, code, and design—remain exclusively with the publisher.

Your entries live locally on your device. Without accounts or central servers, no external copy of your data exists. If a device is lost, wiped, or the app lock passphrase is forgotten, the data cannot be recovered by Cycle0 or anyone else.

Maintaining external backups to secure storage is your responsibility. Restoring a backup requires the exact passphrase set during creation; passphrases cannot be reset. Data handling specifics are outlined in the privacy policy.

Cycle0 aims for reliable performance across supported devices. Features may be added, modified, or retired over time. Operating system updates outside our control may occasionally require maintenance fixes.

Uninterrupted operation, perpetual availability on future operating systems, or permanent inclusion of specific features cannot be guaranteed. While customer support inquiries are reviewed promptly, no strict service-level agreement or turnaround time is guaranteed.

Cycle0 is provided "as is" and "as available," without warranties of any kind, express or implied, including fitness for a particular purpose, defect-free operation, or uninterrupted service. No warranty is made regarding the accuracy of calculated averages or predicted dates. Mandatory consumer rights under Swiss law remain unaffected by this section.

To the maximum extent permitted by applicable law, Cycle0 and its publisher are not liable for indirect, incidental, or consequential damages, lost data, lost profits, or decisions made based on app content or predictions.

Where liability cannot be fully excluded, total aggregate liability is limited strictly to the amount paid for the app. Nothing in these terms excludes or limits liability for gross negligence, willful misconduct, personal injury, or any liability that cannot be excluded under mandatory Swiss law.

Use Cycle0 as a personal log rather than a medical instrument. Keep your device, OS authentication, and app lock secure. When exporting reports or backup files, you control their distribution—once exported, data security outside the app is your responsibility. Use of the app for unlawful purposes is strictly prohibited.

App stores, operating systems, cloud storage services, and external health organizations linked within the app operate independently under their own terms and privacy policies. Cycle0 bears no responsibility for third-party services or content.

You may terminate this agreement at any time by deleting the app. The licence automatically terminates upon a material breach of these terms (such as unauthorized redistribution). Sections 6, 8, 9, and 13 survive termination.

Updates to these terms will be published on this page with a revised effective date, with material changes noted in app release notes. Continued use of Cycle0 following an update constitutes acceptance of the revised terms.

These terms are governed by Swiss law, excluding conflict-of-law principles. The courts of Solothurn, Switzerland have exclusive jurisdiction, subject to mandatory consumer protections in your country of residence that provide alternate jurisdiction. If any provision is found invalid, remaining provisions remain in full force.