Luna vs Euki: on-device privacy or EU-hosted guidance?
Compare Luna and Euki on where data lives, accounts, price, features, and partner sharing. An honest look at a local-only nonprofit app versus an EU-hosted privacy-first one.
Luna and Euki are both on the short list of period apps that take privacy seriously, but they get there in opposite ways. Euki keeps your data on your phone. Luna keeps it on EU servers, so it can offer things that need a cloud, like syncing and a partner mode.
Pattern Snapshot
The fastest way to read this comparison
Euki
A free, open-source tracker run by a nonprofit. It says it never collects personal data, and it also offers sexual and reproductive health information.
Luna
A paid, privacy-first app with EU hosting (Frankfurt), no ads, no data selling, one-tap deletion, a cycle-aware AI, and a privacy-filtered partner mode.
The real difference
Euki minimizes what exists anywhere but your device. Luna stores data in the EU in exchange for more features.
Decision
Pick Euki for maximum data minimization at no cost. Pick Luna if you want guidance, sync, and partner sharing with clear EU hosting.
Competitor details below reflect Euki’s public materials and independent privacy reviews as of October 2026 and can change.
Side by side
| Luna | Euki | |
|---|---|---|
| Where data lives | EU servers (Frankfurt), stated clearly | On your device; its site says it never collects personal data |
| Ads | None | None |
| Data sold or shared | Never sold | States no personal data is collected |
| Price | 1-month free trial, then $4.99/mo | Free, supported by donations |
| Who builds it | Luna Team | An independent nonprofit; open-source project |
| Backup and recovery | Your account lets you restore your data | Local only, so a lost phone can mean lost data |
| Predictions | Ranges with confidence, careful about certainty | Cycle and period tracking with basic predictions |
| AI assistant | Cycle-aware chat from your own logs | No |
| Partner feature | Privacy-filtered partner mode | Not a core feature |
| Account deletion | One tap | Nothing stored on a server to delete |
| Extra content | Cycle education and guidance | Sexual and reproductive health resources |
| Languages | English and French | English and Spanish |
Short answer
Euki is one of the most privacy-minimal options available. Its site says it never collects personal data, and an independent review by Mozilla found that the health information you enter stayed inside the app. It is free, supported by donations, and open source.
The trade-off is built into the design. Data that lives only on your phone is also data that is gone if the phone is lost or reset, and it cannot power things that need a server, like syncing across devices or sharing context with a partner.
Luna makes the opposite trade deliberately. Your data is stored in the EU (Frankfurt), the app runs no ads, never sells your data, and deletion is one tap. In exchange you get account-based recovery, a cycle-aware assistant, predictions shown as ranges, and a partner mode that never exposes your notes, temperature, or intimacy logs.
Neither approach is wrong. They are different answers to the question of how much you want to trust any server at all.
What Euki does well
Euki is built with a clear point of view. It is run by an independent nonprofit as an open-source project, which means the code can be inspected and nobody has a business reason to monetize your data.
It also goes beyond tracking. Mozilla’s review highlights a PIN, automatic data deletion, and a decoy screen for situations where someone might force you to unlock your phone. Those features matter most for people who have real safety concerns about who can see their phone.
It is free, with no premium tier, and it includes sexual and reproductive health information alongside cycle tracking.
If minimizing data is your top priority, or if your threat model includes someone with access to your devices or accounts, Euki is a strong choice and a reasonable fit.
Where the trade-offs show up
1. Local-only means no safety net
If your phone is lost, broken, or reset, local-only data may not come back. There is also no cross-device sync. That is the price of having nothing on a server, and for some people it is exactly the point.
2. A smaller feature set
Euki focuses on tracking and information. It does not offer an AI that reads your own logs or a partner mode. If you want help interpreting patterns, you do that interpretation yourself.
3. Languages and reach
Euki is available in English and Spanish. If you want a French-language experience, that is a practical difference.
Where Luna differs
1. Clear EU hosting with the features that need it
Luna stores data in the EU (Frankfurt), not on an unspecified server. That is what makes recovery, a cycle-aware AI, and partner sharing possible. For what EU hosting does and does not guarantee, see EU hosting for health apps.
2. A business model without ads or data sales
Luna is paid so that it does not have to monetize attention or data. That is a structural difference from free ad-supported apps, explained in privacy-first period tracker vs ad-supported app.
3. A partner mode that stays private
Luna lets you share useful context with a partner while keeping your notes, temperature, and intimacy logs private. If you are weighing that, how partner sharing should work in an app is a good companion read.
4. Honest, range-based predictions
Luna shows predictions as ranges with a confidence level rather than a single exact date. See period predictions are ranges.
Which app is better depending on what you want
If you want the least data possible, at no cost
→ Euki
If you have safety concerns about who can unlock your phone
→ Euki
If you want recovery if you change or lose your phone
→ Luna
If you want a cycle-aware assistant that reads your own logs
→ Luna
If you want to share useful context with a partner without exposing private notes
→ Luna
If you want French
→ Luna
The useful takeaway
Euki makes sense if you want maximum data minimization, you are comfortable with local-only storage, and you value a free, open-source nonprofit app.
Luna makes sense if you want an ad-free app with clear EU hosting, account-based recovery, guidance that admits uncertainty, and a partner mode that keeps private data private.
Both can track a cycle. The better question is whether you would rather trust no server, or trust a clearly stated EU one in exchange for more features.
Is This Normal?
Is an app that stores nothing on a server always more private?
It reduces what a company can ever see, which is a real privacy benefit. It does not remove every risk, because anyone with access to your unlocked phone can still see local data, and a lost phone can mean lost data.
Privacy is a trade-off between exposure and convenience. Local-only and EU-hosted are two different, defensible positions.
Frequently asked questions
Is Euki really private?
Euki’s site says it never collects personal data, and an independent Mozilla review found that the health information entered stayed inside the app, with no account required. Local-only storage also means a lost phone can mean lost data, so back-up and recovery work differently from cloud-based apps.
Is Luna a good Euki alternative?
If you like Euki’s privacy stance but want account-based recovery, a cycle-aware assistant, a partner mode, and French, Luna is built for that. Luna stores data in the EU (Frankfurt) rather than only on your device, and it is paid ($4.99 per month after a 1-month free trial).
Is Euki free?
Euki’s site says it is free to use with no paywalls and is supported by donations. Luna is paid after a 1-month free trial, which is how it avoids ads and data selling.
Does Euki store data on my phone or on a server?
Euki says it never collects personal data, and Mozilla’s review describes data as kept locally on the device. Luna stores data on EU servers in Frankfurt, which is what enables syncing, recovery, and partner sharing.
Does Luna sell my data?
No. Luna runs no ads and never sells your data, and you can delete your account in one tap.
Related reading
- Best private period tracking apps
- How private should a period tracker be?
- Do period apps sell your data?
- EU hosting for health apps
- Euki vs drip: two open-source private period trackers compared
- Period tracker without subscription: how to find one that is genuinely free
If you want a cycle app with no ads, clear EU hosting, and guidance that stays honest about uncertainty, that is what Luna is built for. 1 month free, $4.99/month after, cancel any time.
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Luna is built around concrete guardrails: EU hosting, one-tap deletion, and privacy-limited partner sharing.