28x Ltd

What 28x Ltd does

28x Ltd (operating as 28X) is a UK-based, privately-held health technology company founded by Amber Vodegel — creator of Pregnancy+ (150M+ users, acquired by Philips) — that has developed and publicly launched a free, privacy-first mobile application for menstrual cycle tracking, symptom logging, and women's health education. The product, branded 28X Private Period, is distributed globally through the iOS App Store and Google Play and targets women and girls aged 12-55 (with stated plans to extend coverage to ages 8-50) across 100+ countries, with a roadmap to support 33+ languages including minority languages and three reading levels.

The platform is built on a 100% on-device AI processing architecture: all cycle, symptom, and behavioural data is stored locally on the user's device, encrypted with AES-CFB-128 (keys held in iOS Keychain or Android Keystore following NCSC and NIST guidance), and processed without transmission to any cloud server. The signature AI feature is the Butterfly Digital Twin, which generates a visual representation of the user's cycle, supported by on-device cycle insights and symptom recommendations. Optional Health Sync writes user-initiated data directly to Apple Health or Google Health Connect, with that data then subject to the respective platform's terms. The app achieved a 92% ORCHA rating — described as the highest safety score ever recorded for a period tracking app — and aligns its clinical content with NHS, WHO, CDC, RCOG, and UNICEF guidelines.

28X operates a non-conventional revenue model for a venture-backed health app: the core app is free with no subscription or paywall, and the company explicitly commits to remaining free. Revenue mechanics consist of optional cosmetic in-app purchases (Butterflies visual customisations, processed via Apple/Google with no financial data shared with 28X) and a stated donation-based, mission-driven reinvestment model — the company likens its funding model to Wikipedia. The company is venture-backed via a £1.2M seed round (March 2026) led by the Philips Foundation with 40 angel investors (80% women), with stated use-of-funds including a pledge to open-source the architecture if the model proves successful. App development is delivered through a core partnership with KYAN Media, a Guildford-based digital agency with 40+ specialists.

Name

28x Ltd

Legal name

28X Limited

Website

https://my28x.com

Company type

Private

Founded year

2023

Operating status

Operating

Headcount range

1–10 employees

Short description

28x Ltd operates 28X, a free, privacy-first mobile menstrual health app that processes all data on-device. It targets women and girls aged 12-55 across 100+ countries via iOS and Android, monetising only via optional cosmetic in-app purchases and donations rather than subscriptions.

Ownership category

akta.pro rank

Product category

Women's Health Mobile App (Femtech Software)

NAICS

Computing Infrastructure Providers, Data Processing, Web Hosting, and Related Services (51821)

SIC

Services-Computer Programming, Data Processing, Etc. (7370)

akta.pro primary industry

Women’s Health & Fertility Therapeutics (Digital) (HLACANAK)

akta.pro secondary industry

SaMD – Digital Biomarkers & Algorithmic Endpoints (HLACANAF)

Keywords

• Menstrual cycle tracking
• Period tracking app
• Women's health platform
• Privacy-first femtech
• On-device health data

Headquarters

HQ city

City Of London

HQ country

United Kingdom

HQ region

Europe

Offices1 record

Markets served

GTM type

B2C

Offering type

Software

Cost components

Technology or R&D, Personnel, Marketing or Sales, Operations

Revenue model

1. Donation-Based Model (Wikipedia-style): The app operates entirely free for users, funded by impact-driven donations rather than subscriptions, advertising, or data monetisation. The company describes its model as similar to Wikipedia, where support comes from users and partners who want to advance women's health.
2. In-App Cosmetic Purchases (Butterflies): Optional in-app purchases for visual customisations ('Butterflies') - cosmetic extras that don't affect app functionality. Users can 'buy a new set of wings for your butterfly' and contributions are paid-forward to help bring 28X to women and girls who need it most, including those in low- and middle-income countries.
3. Mission-Driven Reinvestment Model: Operating on a mission-driven reinvestment model, directing profits back into advancing women's health research and education. Supported by impact investors including Philips Foundation and 40 angel investors, with 80% of investors being women.

Pricing tiers

Go-to-market motion3 records

Distribution channels3 records

Marketing channels7 records

Core offering

28X develops and operates a free, privacy-first mobile menstrual health application that tracks cycles, logs symptoms, delivers AI-generated cycle insights via the "Butterfly Digital Twin," and provides medically reviewed educational content. All processing and storage occurs on the user's device using AES-CFB-128 encryption, with no cloud servers, data collection, or data monetization. The app is distributed globally on iOS and Android, with optional user-initiated sync to Apple Health/Google Health Connect and optional cosmetic in-app purchases.

Product overview

28X Ltd offers a single unified product — the 28X Private Period app — which is a free, privacy-first women's health platform built entirely around data privacy. The core app includes the Butterfly Digital Twin as its signature AI-powered visualization feature, which transforms cycle tracking into an intuitive, stigma-free visual experience. Optional add-on features include Health Sync (for syncing with Apple Health or Google Health Connect) and Butterflies visual customizations (optional in-app purchases). The company also provides educational content through 100+ articles and 20+ digital courses. The entire platform operates on a mission-driven reinvestment model with no data monetization.

Differentiator

Problem solved

Functional benefit

Products and services

• 28X Private Period A free, privacy-first mobile menstrual health app for women and girls aged 12–55 that tracks menstrual cycles, logs symptoms, and supports wellbeing while keeping all data stored and processed on the user's device using AES-CFB-128 encryption. Distributed globally via iOS App Store and Google Play with multilingual support and inclusive design.

Quantifiable outcome

• 92% ORCHA privacy rating - highest ever for a period tracking app
• +2 more outcomes

Named customers3 records

Segments4 records

Ideal customer profiles2 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Integration4 records

AI capability4 records

Feature5 records

Partnerships

Eleven partnerships are on record, tiered core, flagship and minor.

• KYAN MediacoreTechnology or IntegrationDigital agency in Guildford, UK leading app development. 40+ specialists across design, engineering, and strategy. Responsible for front-end and back-end development including the Butterfly Digital Twin feature.
• NHSflagshipStrategic or Co-development PartnerContent aligned with NHS guidelines and standards. NHS Service Standard principles followed in product development. The app is designed to support better conversations between users and NHS clinicians.
• Wellbeing of WomenflagshipStrategic or Co-development PartnerResearch partnership focused on designing consent flows, educational content, and participation features. Supports menstrual stem cell research programme advancing women's health research.
• World Health Organization (WHO)coreStrategic or Co-development PartnerHealth information aligned with WHO guidelines and standards. Part of network of leading global health organisations ensuring content accuracy and cultural relevance.
• Centers for Disease Control and Prevention (CDC)coreStrategic or Co-development PartnerHealth information aligned with CDC guidelines. Part of collaboration with major global health organisations for clinically validated, evidence-based content.
• Royal College of Obstetricians and Gynaecologists (RCOG)coreStrategic or Co-development PartnerHealth information aligned with RCOG guidelines and clinical standards. Part of network ensuring medically reviewed, clinically validated women's health content.
• UNICEFcoreStrategic or Co-development PartnerPartnership for global menstrual health advocacy and support. Working on period-related projects and global initiatives addressing menstrual health and hygiene.
• Hello GirlsminorStrategic or Co-development PartnerPartnership addressing period poverty through product donations and support. Contributing to company's mission of making menstrual health accessible to all women.
• Kent Surrey Sussex Health Innovation NetworkcoreStrategic or Co-development PartnerPartnership to gather feedback on how 28X could support better conversations between users and clinicians. Ensures alignment with real-world care pathways and clinical realities.
• The Diana AwardminorStrategic or Co-development PartnerEarly user engagement partnership working with young people to explore attitudes, trust, and expectations around menstrual health, research participation, and digital tools.
• ORCHAcoreStrategic or Co-development PartnerConducted baseline review of the app against ORCHA standards. App achieved 92% ORCHA rating, the highest for any period tracking app, validating privacy and safety architecture.

Scale indicators10 records

Recent moves6 records

Expansion highlights7 records

Direct peers

• Natural Cycles: Natural Cycles is an FDA-cleared digital therapeutic for contraception and fertility tracking. It competes with 28X in the cycle tracking category but operates as a regulated SaMD with a paid subscription, making it a relevant peer for both product overlap and a contrast in regulatory positioning.
• Clue: Clue is a Berlin-based period and cycle tracking app with tens of millions of users and a strong privacy positioning of its own. It is the closest European competitor to 28X and competes on similar scientific rigour, clinical accuracy, and data minimisation messaging.
• Glow: Glow offers a suite of women's health apps covering period, fertility, and pregnancy. Its free-with-premium model and community-led approach make it a relevant direct peer in the same consumer category as 28X.
• Flo Health: Flo Health operates Flo, the world's most-used period and ovulation tracker with hundreds of millions of users. It is the most direct head-to-head competitor in the consumer menstrual health app category, competing for the same target user with a freemium subscription model that 28X explicitly contrasts itself against.

Broad incumbents

• Apple Health: Apple Health includes native cycle tracking and integrates with third-party period apps via HealthKit. As the platform through which 28X distributes via the App Store and to which its optional Health Sync feature writes data, Apple is both a critical partner and a broad incumbent that could deepen native cycle features.
• Ovia Health: Ovia Health is a women's health platform offering cycle, fertility, and pregnancy tracking, now part of Labcorp. It is a broad incumbent with employer and health-plan distribution that competes for institutional women's health budgets in the US market where 28X aims to expand.
• Google Health Connect: Google Health Connect is the Android-side platform for health data aggregation that 28X's Health Sync feature optionally writes to. As a broad incumbent it is both an integration partner on Google Play and a potential competing cycle tracking surface.

Emerging players

• Elvie: Elvie is a femtech brand best known for connected hardware (pelvic floor trainer, breast pump) but has expanded into women's health software and content. It is an emerging player in the broader femtech category with overlapping brand positioning around women's empowerment and design-led product.
• Oura: Oura sells a smart ring with a women's health feature set including cycle tracking, fertile window prediction, and integration with Natural Cycles. It is an emerging player expanding from hardware into cycle insights and competes for the same wellness-conscious user segment.

Others

• Pregnancy+ (Philips): Pregnancy+ is the prior app founded by 28X's CEO Amber Vodegel and now owned by Philips, with 150M+ users. It is the direct lineage of 28X and the most useful internal precedent for product-market fit and scale, as well as the source of the Philips Foundation lead investment.

Market position

Strengths4 records

Weaknesses5 records

Competitive moat6 records

Key risks7 records

Key highlights6 records

Customer concentration

• YouTubeyoutube.com/@28X-private-period
• LinkedInlinkedin.com/company/28x-ltd
• Instagraminstagram.com/28xprivateperiod
• TikToktiktok.com/@28xprivateperiod

Compliance4 records

Revenue estimate

Valuation estimate

Number of profiles

Profiles10 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about 28x Ltd