Summary
Flow Lens is a single HTML file that runs entirely inside the user's web browser. It has no server, no backend, and no data transmission. The CSV file you load into it never leaves your machine under any circumstances.
Data handling
| Question | Answer |
|---|---|
| Is the CSV uploaded to any server? | No — read by the browser's File API into memory only |
| Is any data transmitted over the internet? | No — CSV data never leaves the device |
| Is any data written to disk or browser storage? | No — no localStorage, cookies, or IndexedDB writes |
| Is data retained after closing the tab? | No — all data is discarded on tab close |
| Does the tool collect analytics or telemetry? | No — no analytics, no usage tracking, no error reporting |
| Is a login or account required? | No |
| Does it make any network requests? | No — fully self-contained, works offline immediately |
| Can it be used offline? | Yes — always, with no setup required |
Network activity
The tool is a single self-contained file. No CDN, no external dependencies, no internet connection required — ever.
Libraries bundled inside the file
The following open-source libraries are embedded directly in flow-lens.html at fixed versions:
User-initiated links — only when clicked
The tool contains links to an online user guide and the author's website. These open in a new browser tab only when explicitly clicked by the user, and carry no data.
Risk assessment
| Risk | Level | Notes |
|---|---|---|
| Data exfiltration to a remote server | None | No outbound data calls exist in the code |
| Data persisted on the user's machine | None | No storage writes of any kind occur |
| Unauthorised access to data | None | No server, no shared instance, no login — data exists only in a single local browser session |
| Supply chain compromise via CDN | None | No CDN is used — libraries are bundled at fixed versions inside the file. No external code can be injected. |
| Installation of software | None | No installation required — it is a single file opened in a browser |
Independent verification
Anyone with browser developer tools can verify these claims without trusting this document:
- Open
flow-lens.htmlin Chrome or Edge. - Open Developer Tools (F12) and go to the Network tab.
- Drop a CSV onto the page and interact with the charts.
- Confirm that no network requests are made after the initial library loads — and that no requests contain CSV data.
All application logic is plain JavaScript inside the single HTML file and is fully human-readable. The source code is publicly available at github.com/Simeon-techbss/flow-lens.