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How to verify that GISConverter never uploads your file

By Ghulam Hasnain · PhD researcher, Space Science & Technology · · 4 min read

Plenty of converters say your data is private. This guide shows how to check it, using the network inspector built into every browser. It takes two minutes and needs no technical background.

Why a claim is not enough

The whole point of GISConverter is that survey points, client parcels and unpublished site boundaries never leave your machine. You should not have to take that on trust. Every browser can list every network request a page makes, so you can watch a conversion happen and confirm that your file is not one of them.

This works because the conversion engine, GDAL/OGR, has been compiled to WebAssembly and runs inside the tab. There is no server to send the file to.

Open the network inspector

Tick Preserve log so the list is not cleared, and clear it once so you start from an empty table.

Convert a file and watch the list

  1. Open any converter page, for example KML to Shapefile.
  2. Drop a file. Use a real one, or download a sample KML first.
  3. Pick the output format and click Convert.
  4. Click Download.

Now read the Network table. Every row is one request. Two columns matter: Method and Size.

What you will see

Requests that are normal

What you will not see

The download itself starts with blob: in its address. That is a file held in your browser's memory, handed to you directly. It never passes through a server, and it is gone when you close the tab.

A second check: go offline

After one conversion has finished, the engine is loaded. In the Network tab, switch the throttling menu to Offline (Chrome and Edge) or use your system's flight mode. Then convert another file. It still works. A converter that depended on a server could not do that.

The map preview will lose its basemap while you are offline, because the tiles are the one thing that does come from the network. Your features still draw.

Why it is built this way

GDAL/OGR is the open-source library behind QGIS and most professional GIS software. GISConverter uses a build of it compiled to WebAssembly, a format browsers can run at close to native speed. Instead of moving your data to where the software is, the software moves to where your data already is. That makes the tool free to run at any scale, and it makes the privacy promise something you can test rather than something you have to believe.

Frequently asked questions

Does the map preview send my data anywhere?

No. The basemap tiles are requested by zoom level and tile position, and your features are drawn on top of them inside the browser. The tile server can infer roughly which area you are viewing, but it never receives the coordinates, attributes or shapes in your file. If even the area is sensitive, go offline after the engine has loaded and convert without the basemap.

Why does the first conversion download a few megabytes?

That download is the GDAL engine itself, compiled to WebAssembly. It is fetched once from a content delivery network, cached by your browser, and reused for every later conversion, including offline ones.

Does the site keep logs of what I convert?

It cannot. There is no server that processes files, so there is nothing to log. As the privacy policy explains, the hosting provider keeps standard access logs (your IP address and which pages you opened), the same as any website.

Can I run this check on a phone?

Mobile browsers hide the network inspector, so the easiest check on a phone is the offline one: convert a file once, switch on flight mode, and convert another. It still works because the engine is already on your device.

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About the author

Ghulam Hasnain is a PhD researcher in space science and technology who works with GIS and remote-sensing data every day, wrangling shapefiles, KML, GPX and CAD drawings across QGIS, ArcGIS and Google Earth. He built GISConverter after one too many format conversions that required uploading sensitive survey data to a stranger's server.