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The world’s first women's health app built entirely around privacy

What we did

App Development
Mobile App
Branding

Client

28X

Hands holding an iPhone showing the 28X app, with a green butterfly companion over a sunset landscape on the 'Spring Season, Day 7' home screen.

We partnered with 28X to design and build something genuinely new. A period tracking app that puts your data in your control

Most health apps are built on the quiet trade-off of your data for their service. 28X wanted to break that model entirely and track menstrual cycles with clinical accuracy, not share data and meet medical compliance standards. And it had to be delightful to use.

Two iPhones on a dark purple background — one showing a pink butterfly in a mountain landscape for the 'Late Luteal' phase, the other showing a health insight article.
Editorial portrait of two women on a pink background with the yellow serif headline 'Built for Everyone' and the 28X butterfly emblem.
Close-up of the 28X flow tracking screen with a weekly calendar, butterfly markers under each day, and flow level options from spotting to flooding.
Three iPhones on a purple background showing the 28X tracker calendar, a body-sensation questionnaire, and an 'Autumn Season, Day 14' home screen with a pink butterfly.
Top-down lifestyle photo of a woman's hand on yellow fabric, overlaid with a 'Previous Cycles' card showing recent cycle lengths.
Bold yellow serif typography on a dark purple background reading 'Strong, Confident, Flow, Feeling, Modern' alongside a delicate butterfly illustration.

The Big Idea

We built a privacy-first architecture where everything lives locally on the user's device, fully encrypted. Instead of the usual dashboard of charts, we created a brand and digital experience that evolves with you: a visual companion that responds to your cycle in real time. It's data-driven, but genuinely beautiful.

Three iPhones on a dark background showing the butterfly customisation gallery with Home, Neon, and Calm butterfly variants across seasonal landscapes.
Close-up of a woman's neck and shoulder with the 28X 'Period Journal' mood tracker overlaid, showing a weekly bar chart of moods.
A hand holding an iPhone showing the 28X 'Winter Season, Day 28' home screen with a pink butterfly over a moonlit mountain landscape.
Tilted grid of 28X app wireframes showing setup forms, cycle history, journal entries, and a 'Donate your data' screen.
Three 28X app cards on a pink background showing a hormone level graph, an educational article on FSH during menstruation, and the cycle calendar.
Lifestyle photograph of a couple's hands resting together on a partner's stomach.
Tilted grid of 28X content cards including health insight articles on cycle mechanisms and oestrogen, mood tracking, and the 28X butterfly logo.

The Results

After lots of hard graft and multiple algorithm rebuilds we have a new technical blueprint for privacy-first health apps, with a white paper in the works to share what we've built.

Composition of 28X app screens showing the cycle tracker, 'Private period' editorial portraits, and 'Made by women' branding.
An iPhone displaying a 28X health education slide with a smiling woman in a denim jacket and the caption 'Knowing your breasts can help you spot signs of cancer early'.
Overhead lifestyle photograph of a woman lying down beside a houseplant, overlaid with the 28X weekly calendar showing tracked period days.

Kind Words

Kyan has been an exceptional partner across strategy, design and engineering. Their ability to translate complex ideas into a beautifully executed, high-performance product has been instrumental in bringing 28X to life.

28X

Amber Vodegel

CEO & Co-Founder, 28X

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