Privacy Policy

Last updated: 2026-10-30

MermaidStudio is an open-source Mermaid diagram editor. This policy covers both the web application and the Android application.

The short version

MermaidStudio is local-first: your diagrams are stored on your device and never sent to us. We run no accounts and no servers. The public website uses Vercel's cookieless analytics (see Analytics below). The only third party that processes data is Google, through the ads shown in the Android app — and you control that with a consent form.

Data storage (web and Android)

• Diagrams, folders, versions, tags, and settings are stored locally on your device (browser IndexedDB, or the app's local storage on Android).
• Nothing is uploaded to us. There is no account system and no sync service.
• Exports (PNG/JPEG/SVG) are generated on your device and shared or saved only where you choose (e.g. the Android share sheet or your photo library).

AI features (web)

AI assistance runs in your browser on your own device (WebGPU-based local inference). Prompts and diagrams used by the AI features are processed locally and are not sent to us or to any external service.

Analytics (web)

The public website measures aggregate, anonymous usage with Vercel Analytics and Vercel Speed Insights: page views, referrers, and coarse geography. These analytics are cookieless — no cookies, no localStorage, no advertising identifiers, no cross-site tracking — and we cannot identify individual visitors.

Ads (Android only)

The Android app shows ads via Google AdMob (Google Mobile Ads SDK):

• Google and its partners may collect and process the advertising identifier (AD_ID) and related ad-interaction data to serve and measure ads, under Google's Privacy & Terms and the Google AdMob program policies.
• Before any ads are initialized, the app asks for your consent with Google's UMP consent form (GDPR). You can review or change your choices at any time via Settings → Privacy options in the app.
• You can also turn ads off entirely with the Ads toggle in Settings; the change takes effect immediately.

What we never do

• We never sell your data.
• We never transmit your diagrams off your device.
• We have no access to your diagrams or settings. (Aggregate, anonymous site metrics are covered in Analytics above.)

Changes to this policy

Material changes will be updated in this document with a new "last updated" date.

Contact

Open an issue at github.com/CatFoxVoyager/MermaidStudio/issues.