Telemetry, analytics and document transfer are not the same
Finding network connections in the browser's Network panel is not enough to conclude that a PDF tool uploads your document. A website can send statistics, errors or navigation events without sending the PDF itself.
The essential idea
Network traffic is not the same as document transfer. Determine whether a PDF leaves the device by examining request size, content, type, destination and timing.
Three concepts to keep separate
1. Telemetry
Technical information about application behaviour such as errors, loading times, performance, browser version or operational events.
2. Analytics
Measures website use such as pages visited, navigation, clicks, language, referrals or aggregate events. It can create network traffic without containing the PDF.
3. Document transfer
Occurs when the full PDF, parts of it or sufficient derived document data are sent outside the device for storage, processing or another purpose.
A small request usually does not look like a PDF upload
An analytics event may be hundreds of bytes or a few kilobytes. Document transfer commonly produces much larger requests, although sizes do not always match the original file.
Why request size may differ
- multipart/form-data adds headers and boundaries.
- Base64 can increase data size.
- Files may be compressed before transfer.
- Uploads can be split into chunks.
- Only pages, images, text or derived data may be sent.
- Several fields may be bundled in one request.
What to inspect in Network
| Method | POST and PUT deserve attention, although other methods may also carry data. |
|---|---|
| Size | A request close to PDF size or a sequence of large requests is relevant. |
| Content-Type | application/pdf and multipart/form-data are useful clues, but documents can be encoded differently. |
| Payload | When visible, it can reveal whether the request contains a file, text, metadata or only an event. |
| Destination | Endpoints such as upload, file, document, convert, storage or process deserve inspection. |
| Timing | Check whether the request appears when selecting the PDF, starting processing or simply loading the page. |
| Initiator | Shows which script triggered a request and may help distinguish analytics from processing. |
Watch for chunked uploads
Do not look only for one huge request. Some systems split a document into smaller blocks. Consecutive requests whose combined size approaches the file may represent one upload.
Telemetry is not automatically harmless
A request that does not contain the complete PDF can still have privacy implications. Poorly designed telemetry might include file names, identifiers, URLs, text or other sensitive metadata.
What about blob: URLs?
A blob: URL usually references data available within the browser context. It can be useful evidence, but it does not prove that an earlier server upload never occurred.
Offline testing helps separate scenarios
Load the tool first, disconnect, and only then select the PDF. If the operation completes with a valid result, that strongly supports a server-independent workflow for the tested operation.
Conceptual examples
| Analytics event | 1.8 KB POST to /analytics containing an event type and page. | Does not prove PDF transfer. |
|---|---|---|
| Error telemetry | 4 KB POST with browser version and error message. | Does not prove PDF transfer. |
| Document upload | Multi-megabyte multipart/form-data POST immediately after file selection. | Strong evidence of document data transfer. |
| Chunked upload | Twenty consecutive requests of hundreds of KB to an upload endpoint. | May represent a divided upload and should be analysed together. |
How this applies to PDFPrivado
PDFPrivado can handle aggregate navigation metrics separately from document content. In the published processing tests, all 14 audited tools completed their workflow after preloading and disconnecting, and the equivalent online control observed no document transfer during processing. A fully offline cold start was not tested.
Related guides
Frequently asked questions
Does every POST request mean my PDF is being uploaded?
No. POST is used for many data types. Inspect size, content, type and destination.
Can a tiny request contain my whole PDF?
A normal PDF is unlikely to fit in a much smaller request, but fragments, extracted text, metadata or derived data could be sent.
Can I rule out an upload if no request matches the exact PDF size?
No. Files can be compressed, encoded or divided into multiple requests.
Is analytics the same as document transfer?
No. They are distinct categories, although analytics should also be designed with privacy in mind.
Published and verified: September 7, 2026