Who builds Crimson
Crimson is built and operated by Driftline Ventures LLC, the company behind both the app and this website. We answer our own support email: reach us any time at support@getcrimson.app.
Why we built it
Cycle tracking should work for you, not for advertisers. Most period apps treat your body like a data mine. We built Crimson around the opposite idea: private-by-design tracking for every stage, from first periods through perimenopause, with AI that helps you make sense of what you log.
No guesswork. No pink-washed nonsense. Just your data, working for you.
How we handle your data
Health data deserves more than a checkbox. Our stance, in plain terms:
- Local-first. Your data lives on your device first, and syncs to the cloud so it survives a lost phone.
- Encrypted sync. Cloud sync runs on Convex with TLS 1.2+ encryption in transit and encryption at rest. We do not offer end-to-end encryption, and we will not pretend otherwise.
- Never sold. We do not sell, share, or monetize your health data. Full stop.
- AI without homework. The AI assistant works out of the box. The provider key is configured on our servers, so you never paste an API key into anything.
- Yours to take. Export your data as CSV (with date filtering) or as PDF cycle and pregnancy reports, free, any time. Delete your data any time, too.
The full details live in our Privacy Policy.
How we write about health
The health content on this site is written by the Crimson team. It is grounded in established clinical guidance, including patient education from the American College of Obstetricians and Gynecologists (ACOG), and every page is reviewed before it goes live. When clinical guidance changes, we update the content to match.
What you read here is educational, not medical advice. It is meant to help you have better conversations with a qualified healthcare provider, not to replace one. Last updated: July 25, 2026.
The app
Crimson is free to download, with an optional Crimson Pro subscription (every new account starts with a 14-day Pro trial, and Pro adds unlimited AI). One app, four modes, 70+ trackable symptoms:
Cycle tracking
Periods, symptoms, moods, and predictions that sharpen with every logged cycle.
Trying to conceive
Fertile window and ovulation predictions built on your actual cycle history.
Pregnancy
Week-by-week tracking with kick counts, contractions, appointments, and reports.
Perimenopause
Hot flashes, hormone results, and pattern spotting through the transition.