Privacy Policy

1.Who we are

SQUARE3 Limited (referred to as “Sentra”, “we”, “us”) is the data controller for personal data processed in connection with the Sentra app, its spot walking features, and the website at sentra.city (the “Service”).

• Registered office: 92 York Street, London, England, W1H 1QX
• Company number: 16466339
• General privacy enquiries: legal@sentra.city

2.Our privacy promises

Sentra is built on privacy by design and by default (Article 25 UK GDPR). Specifically:

• Anonymous by default. You can look around without an Account.
• We aim to host personal data primarily in the UK, although some service providers may process limited data outside the UK as explained in section 8.
• Data minimisation. We collect only what is necessary for the feature you are using.
• We retain data only for as long as necessary, generally up to 90 days unless longer retention is required.
• Industry-standard encryption and security measures.
• We do not sell your personal data. An individual location trace is not a product, in any form and at any price.

3.What data we collect, why, and on what lawful basis

3.1 Account creation and verification

If identity verification is used, this is handled by our third-party verification provider under their own privacy terms.

3.2 Location data

Location is the most sensitive category we handle, and Sentra is a walking app, so we treat it accordingly. The point of reading your location is to tell that you actually reached a place on foot, rather than that you pressed a button saying you did.

You control location permissions through your device settings and can switch them off at any time. If you do, presence checks stop working and the rest of the app continues.

3.3 Content you submit

We may keep anonymised statistics after deletion so we can identify broader trends. See section 3.6 for the threshold that applies before any of it leaves.

3.4 Device, app, and analytics data

We do not use third-party advertising trackers, Meta Pixel, or cross-site/cross-app tracking SDKs. There is no advertising-ID-based profiling.

3.5 Communications

We will only send you marketing if you have specifically opted in (PECR / soft opt-in). Every marketing email contains a one-click unsubscribe.

3.6 Aggregated and anonymised data

We may use anonymised and aggregated data for analytics, service improvement and business reporting. This data does not identify individual users.

4.Special category data

We do not intentionally collect special-category data (health, ethnicity, sexual orientation, religion, political views, trade-union membership, biometric or genetic data).

Applying that to a walking app specifically: we do not build a gait template, a movement fingerprint or any other biometric profile of you. That would be special-category data under Article 9 UK GDPR, and we have no basis for holding it and no intention of collecting it.

If you submit content that incidentally includes special-category data (for example, a description of a person that mentions their ethnicity), our moderation policy is either to redact the identifying details before display, or to ask you to resubmit without those identifiers and delete the preceding submission.

5.Who we share data with

We share personal data only with the parties listed below, and only for the purposes described.

5.1 Sub-processors (act on our instructions)

5.2 Third-party data sources

This is their data coming in, not your data going out. The Service does not currently ingest data from third-party data sources. If this changes in future (for example, if we integrate a public-sector data feed or a place-data provider), this Policy will be updated and any new sub-processors added to the list in section 5.1.

5.3 Disclosures to law enforcement

We may disclose personal data where required by law or where necessary to protect users or others from harm.

5.4 Corporate transactions

If Sentra is involved in a merger, acquisition, or sale of assets, personal data may be transferred to the successor controller, subject to confidentiality obligations and the same protections as this Policy. We will notify users of any change in controller.

Individual location traces are excluded from any such transfer. They are deleted rather than transferred. Only data that has been aggregated to the threshold in section 3.6 may pass to a counterparty. This holds without exception: section 3.6 says an individual location trace is never made available to a third party in any form, and a corporate transaction does not create one.

Investors are not successor controllers. We do not transfer personal data as part of a financing round, due diligence exercise, or any similar process.

5.5 We do NOT

• sell your personal data;
• share it with advertising networks for profiling or behavioural advertising;
• use it to train third-party AI models;
• share an individual location trace with anyone, including your university.

6.Advertising

If advertising features are introduced in future, this Policy will be updated accordingly, and we will obtain your consent under PECR before introducing any advertising that uses cookies or device identifiers for tracking purposes.

7.Your rights under UK GDPR

You have the following rights, exercisable free of charge in most cases:

• Access — request a copy of the personal data we hold about you.
• Rectification — correct inaccurate data.
• Erasure (“right to be forgotten”) — delete your data, subject to legal retention requirements.
• Restriction — limit how we process your data.
• Portability — receive your data in a structured, machine-readable format.
• Object — object to processing based on legitimate interest, including profiling.
• Withdraw consent — at any time, where we rely on consent. Withdrawal does not affect the lawfulness of processing before withdrawal.
• Right not to be subject to automated decision-making, where it produces legal or similarly significant effects on you. We will provide human review on request.
• Complaint to the ICO — as shown in section 15.

To exercise any right, use in-app Settings → Privacy → Data Rights, or email legal@sentra.city with the subject line “Data Subject Request”. We will respond within one calendar month (extendable by two further months for complex requests, with notification). We may need to verify your identity before responding, especially for access and erasure requests.

8.International transfers

Personal data is stored in the UK by default. Some sub-processors (Google, Mapbox and others) may transfer data to the EEA, US, or other jurisdictions for technical reasons (for example, global CDN nodes). Where personal data is transferred outside the UK, we implement appropriate legal safeguards.

9.Retention

We retain personal data only as long as necessary:

• Account data: while your Account is open, plus 30 days for safe deletion.
• Submitted content and the location attached to it: 90 days as raw data, then auto-deleted. Aggregated and anonymised statistics may persist indefinitely, subject to the threshold in section 3.6.
• Billing and tax records: 6 years (HMRC requirement).
• Legal holds: if data is subject to a court order or active dispute, we retain it until the matter is resolved.
• Marketing consents: until you opt out.
• Logs: 30 days (security and access logs).

Deletion runs on a schedule rather than on request: when the retention period ends, data is securely deleted or genuinely anonymised.

10.Security

Our technical and organisational measures include:

• Encryption: AES-256 at rest, TLS 1.2+ in transit.
• Access controls: role-based access, multi-factor authentication for staff, least-privilege.
• Hosting: UK regions only by default.
• Network security: WAF, DDoS protection, intrusion detection.
• Vulnerability management: dependency scanning, regular penetration tests, and a responsible disclosure programme at legal@sentra.city.
• Staff training: mandatory privacy training for all staff with access to personal data.
• Incident response: documented breach response plan with 72-hour ICO notification for personal-data breaches likely to result in risk to users (Article 33 UK GDPR).
• DPIA: completed before launch and reviewed annually, plus on any material change.

No system is 100% secure. We will notify you and the ICO of a personal-data breach in line with our legal obligations.

11.Children

The Service is not directed at children. If you believe an individual under 18 has used the Service, contact legal@sentra.city and we will delete the account and associated data.

12.Cookies and similar technologies

The Sentra app does not use tracking, analytical, or third-party cookies, pixels, or tags. We may use strictly necessary functional cookies or similar device storage (for example, for session continuity, security, and core app functionality). These are exempt from the consent requirement under regulation 6(4) of the Privacy and Electronic Communications Regulations 2003 (PECR).

For the website you are reading now, see the cookie policy.

13.Anonymous mode — what we do and don’t see

When you use Sentra in anonymous mode (no Account):

• We do not collect: your email, name, payment data, or any data linked to a stable identity.
• We do see: device type, app version, IP address (for security and abuse prevention only — not retained against an identity), and approximate location while the app is in use.
• We do not combine anonymous-mode session data with Account data.

14.Changes to this Policy

We may update this Policy. The “Last updated” date at the top will always reflect the current version.

What changed in version 2.1 (3 August 2026):

• Section 3.2 now describes location processing in terms of the spot walking features — the daily shared destination, cap pickups and the two-sided co-walk streak — instead of the earlier feature set. The permissions, the controls and the retention position are unchanged.
• Section 3.6 states the aggregation threshold explicitly as k ≥ 5 and adds that individual location traces are never sold or shared.
• Section 4 states expressly that no gait template or movement fingerprint is built.
• Section 5.4 now excludes individual location traces from any corporate transaction: they are deleted rather than transferred, and only data aggregated to the section 3.6 threshold may pass to a counterparty. Financing rounds and due diligence are removed from the clause entirely — an investor is not a successor controller. This narrows what we may do with your data; it does not widen it.
• Section 9 clarifies that deletion runs on a schedule.

15.Contact

• Privacy and data subject requests: legal@sentra.city
• Postal: 92 York Street, London, England, W1H 1QX, United Kingdom

If you have a complaint that we cannot resolve, you have the right to lodge it with the Information Commissioner’s Office (ICO): ico.org.uk, or call 0303 123 1113.