Privacy Policy

Last updated: 2026

What we collect

When you upload a CGM data file and generate a report, we record the following anonymized statistics about the job:

• Timestamp of the job (UTC)
• File format detected (e.g., Dexcom Clarity, Tandem t:connect)
• Report type requested (daily or dashboard)
• Date span of the file, in days
• Number of sensors and transmitters detected
• Aggregate glucose statistics: mean glucose, estimated A1c, time below 70 mg/dL, hypoglycemic event count
• Sensor integrity metrics: cluster count, cluster rate, post-cluster hypoglycemia count
• CGM device type (e.g., G6, G7) and AID algorithm if detectable
• Processing time in milliseconds
• Approximate geographic region: country and US state, derived from your IP address via Cloudflare headers
• Algorithm version string

What we do NOT collect

• Your IP address — it is not stored in our database
• Your name or any identifying information from your file
• Your filename
• Individual glucose readings
• Any data that would allow us to reconstruct your glucose trace

Your uploaded file

Your file is written to a temporary session directory on our server for the duration of your session. It is deleted automatically after 30 minutes of inactivity. It is never copied, shared, or retained beyond your session. No glucose values from your file are written to our database.

How aggregate data is used

The anonymized statistics described above are used to power a private analytics dashboard that tracks aggregate CGM sensor performance trends across device types and geographic regions. This data may be referenced in published research or journalism in aggregate, anonymized form only.

Cookies

We use a single session cookie to associate your uploaded file with your browser session. It contains no personal information — only a random session identifier. It expires when you close your browser or when your session times out.

Third parties

This site uses Cloudflare for DNS, CDN, and DDoS protection. Cloudflare may log your IP address in accordance with their own privacy policy. We do not use advertising networks, analytics services, or any other third-party data collection.

Contact

Questions about this policy can be directed to danheller.substack.com.