Clue vs Flo vs Glow: Privacy Compared Across Three Major Period Trackers

Clue vs Flo vs Glow vs Floriva: Privacy Architecture
Feature	Clue	Flo	Glow	Floriva
On-device storage	No	No	No	Yes
Account required	Yes	Yes	Yes	No
FTC enforcement	No	Yes (2021)	No	No
Data can be subpoenaed	Yes	Yes	Yes	No
Ad-supported free tier	No	Yes	Yes	No
GDPR compliant	Yes	Yes	No	N/A
Price	Free / $9.99/mo	Free / $4.99/mo	Free / $79.99/yr	$2.99/mo

Three mainstream apps, one structural problem

Clue, Flo, and Glow dominate the period tracker category by download volume. All three require an account. All three store your data on their servers. The differences are in their track records and business models.

Flo is the largest by user count and has the worst enforcement record. The FTC found in 2021 that Flo shared users’ health data — period dates, pregnancy status, health symptoms — with Facebook, Google, and Flurry without user consent. A class action over the same conduct settled for $59.5M in September 2025 (Reuters 2025-09-25). Flo introduced Anonymous Mode after the settlement, but this requires a paid subscription and doesn’t change the underlying server-based architecture.

Clue is the strongest option of the three on privacy. Berlin-based, GDPR-compliant, no documented data-selling enforcement history. The free tier has no ads. But GDPR compliance is a policy control — it limits commercial data use, it does not prevent law enforcement access. Your data is still on Clue’s servers.

Glow is ad-supported and free, covering fertility, pregnancy, and parenting features beyond basic cycle tracking. No documented FTC enforcement. But the ad-supported model typically involves data use, and Glow stores everything server-side.

Why none of them solve the structural problem

The issue with all three apps is not primarily policy — it’s architecture. When your period data lives on a company’s server, linked to your account, it can receive a subpoena. In states with abortion restrictions, prosecutors have sought digital evidence including period tracking data. Privacy policies and GDPR compliance mitigate commercial misuse but do not prevent legal compulsion.

On-device-only trackers (Floriva, Drip, Euki) take the data off the table by never putting it on a server in the first place.

Pricing snapshot

Clue: Free / $9.99/mo. Flo: Free / $4.99/mo. Glow: Free / $79.99/yr. Floriva: $2.99/mo, on-device storage default for all users.

Neither feels private enough?

Floriva stores everything on your device. No data sold, no account required.

Verdict

Among Clue, Flo, and Glow, Clue has the best privacy track record. Flo has the worst — an FTC enforcement action and a $59.5M class action. Glow is free but ad-supported with a freemium upsell model. All three store data server-side with no on-device-only option. For structural privacy, none of them provides it.

PROS & CONS

Clue

Pros

Cleanest enforcement record of the three
GDPR compliance with Berlin headquarters
Ad-free on free tier

Cons

Still requires account and server storage
Data technically accessible via legal process
Premium required for full features

PROS & CONS

Flo

Pros

Largest dataset for cycle prediction accuracy
Feature-rich on free tier
Wide platform availability

Cons

FTC-confirmed data sharing with Facebook and Google (2021)
$59.5M class action settlement (2025)
Privacy mode is paywalled
Server-based with subpoena exposure

PROS & CONS

Glow

Pros

Free with fertility, pregnancy, and parenting features
Community forums for peer support
Broad health tracking beyond cycles

Cons

Ad-supported — business model tied to data use
Requires account and server storage
No on-device option
Less strong privacy positioning than Clue

Is Clue or Flo better for privacy?

Clue is better for privacy than Flo based on enforcement record. Flo had an FTC action in 2021 for sharing health data with Facebook and Google without consent, and a $59.5M class action settled in September 2025. Clue has no comparable enforcement history and operates under GDPR. Neither app offers on-device storage — both can technically be subpoenaed.

Does Glow sell period data?

Glow has not faced the same documented FTC enforcement as Flo or Premom. However, Glow's free tier is ad-supported, which typically involves some degree of data use for advertising purposes. Glow stores data server-side and requires account creation. Users concerned about reproductive data exposure should review Glow's current privacy policy directly.

What period tracker stores data only on your device?

Floriva stores all cycle data exclusively on your device using encrypted local storage — no account required, no server transmission. Drip (Android) and Euki also use on-device storage as default. Clue, Flo, and Glow all require accounts and store data on company servers.

Frequently Asked Questions

What is the difference between Clue and Flo?

Clue is Berlin-based and GDPR-compliant with no documented data-selling enforcement history. Flo is the largest period tracker by user count but faced FTC enforcement action in 2021 for sharing user health data with Facebook, Google, and Flurry without consent. A class action over the same conduct settled for $59.5M in September 2025. Both apps require accounts and store data server-side.

Is Glow a good period tracker?

Glow is functional and free, covering periods, fertility, pregnancy, and parenting. The ad-supported business model raises data-use questions that are common to free apps in the femtech space. Glow does not have FDA clearance for contraceptive use and is not architecturally private. For basic cycle tracking at no cost with better privacy posture, Euki is worth considering.

Can period tracker data be subpoenaed?

Any data held on a company's servers can potentially be subpoenaed. Clue, Flo, and Glow all operate server-based storage — a court order can compel them to produce user data. Apps using on-device-only storage (Floriva, Drip, Euki) cannot hand over data they do not hold.

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