28X is a free to use, privacy-first women’s health app. It helps you understand your body without giving up your privacy. It’s a simple menstrual health companion that tracks your cycle, logs your symptoms, and supports your wellbeing, all while keeping your data safely on your device, rather than in the cloud. This makes that you are in full control of your own data. Our mission is to give every woman, everywhere, access to trustworthy, science-based information without ever compromising personal data.

Search for “28X Private Period” on the App Store [iOS] or Google Play [Android] and tap download. The app is lightweight, secure, and available globally with no subscription and no hidden fees. You can also use the download buttons on this website to go straight to the correct store page.

Yes. We believe menstrual health is a right, not a privilege, and women’s health should never sit behind a paywall. 28X is supported by impact-driven partners rather than advertising or user data, which means it will always remain free to download and free to use.

We protect what others monetise. Many period apps collect, store, and share your intimate data. 28X doesn’t. We don’t run ads, we don’t share data, and we don’t store anything in the cloud. 28X is completely free to use, and we use technology to empower you, not exploit you.

Because your health data should never be for sale. Women’s health data has been exploited for far too long, and we want to change that. 28X is built so you never need to trade privacy for convenience. Your information stays on your device at all times, and it never leaves it, not even anonymously, unless you want to share it.

Never. Your data is processed on your device only, and it’s never uploaded to any cloud or shared with advertisers, governments, or third parties. No tracking, no sharing, and no hidden clauses. Ever. If you choose to share your information with someone, that’s entirely up to you and always on your initiative.

Yes, instantly. Your data belongs entirely to you. You can delete it at any time, and because nothing is stored online, it’s gone for good, not archived, not retrievable, not copied anywhere.

28X doesn’t share your information automatically. You decide if you want to export or share specific data with your doctor or another app, the choice is 100% yours.

Every woman, everywhere. Whether you’re 12 or 50, in London or Lagos, with regular cycles or unpredictable ones, 28X adapts to you. The app will be available in many languages and is designed to support different reading levels and neurodivergent users, making it accessible to as many people as possible.

Absolutely. 28X is built with inclusivity at its core, adaptable for three reading levels, with accessible visuals, calm colours, and compatibility with screen readers.

28X is built by women, for women, united by one belief: Women’s health is public health. We’re backed by impact investors, 80% of whom are women, and we reinvest our profits directly into advancing women’s health.

All our educational content is medically reviewed and aligned with trusted national guidelines. In the UK, that means NHS-aligned information. In every other country, we work with local medical advisors and nonprofit health organisations to ensure the content is accurate, evidence-based, and culturally relevant. Everything is written in clear language so it’s accessible for all reading levels.

We inform, not diagnose. 28X is not a medical device and it doesn’t replace professional care. Our purpose is to improve health literacy for every woman, everywhere, using clear and clinically validated information. If you ever need more support, the app will guide you towards the right pathway or a qualified healthcare professional.

It’s a new way to understand your cycle. The Butterfly Digital Twin uses AI to reflect your body’s natural rhythms in a gentle, visual way that feels human rather than clinical. It’s designed to be culturally sensitive and age appropriate, so it feels comfortable and relatable for everyone. Everything is processed privately on your device, with no data stored externally. It turns your cycle into something you can see, understand, and connect with at a glance.

Only when it helps. We don’t use AI because it’s trendy, we use it to solve real problems. Every innovation must answer one question: does this genuinely improve her life? If not, it doesn’t make the cut.

It’s simple. We designed it to be affordable to run. 28X processes everything safely on your phone using on-device AI, which means we have hardly any operating costs and can keep the app free for everyone, everywhere. Impact investors and users who choose to pay it forward help us make sure it stays that way.If you ever want to support other women and girls, you can simply buy a new set of wings for your butterfly. Your contribution is paid-forward to help bring 28X to the women and girls who need it most, including those in low- and middle-income countries