How to convert GIS files privately in your browser
Once a file has been sent, you cannot unsend it. Most online tools make you upload your data before they convert it. You can convert GIS files privately in your browser instead. This guide explains how that works, why it matters, and how to check that a tool keeps your files on your device.
Key facts
- Conversion runs entirely in WebAssembly on the client, so 0 bytes of your file are transmitted.
- The tool covers 48 format pairs across vector, CAD, GPS and tabular data.
- There is no file-size limit beyond available browser memory, and it works offline once the engine has cached.
The problem with uploading
Most converters work the same way: you upload a file to their server, they process it, and they send the result back. Your data has left your device at that point, and you no longer control it.
Why GIS data is sensitive
Spatial data is often private: client sites, survey points, protected habitats. Uploading it to an unknown server can breach an agreement before anyone has even looked at the map, and from the outside you cannot see what happens to a file after it arrives.
How in-browser conversion works
Modern browsers can run a full conversion engine inside the tab. The engine here is GDAL, the library behind most desktop GIS software, compiled to WebAssembly.
- You drop a file on the converter page, exactly as you would anywhere else.
- The browser reads the file into memory, without sending a single byte out.
- The engine converts it right there on your machine.
- You get a download, generated locally and handed straight to you.
At no point does the file travel across the network. A large file takes longer on a slow machine, but it still never leaves that machine. The same engine handles many formats locally, including Shapefile to KML, KML to GeoJSON and DXF to KML.
What you gain
| Benefit | Why it follows |
|---|---|
| Privacy | Nothing is uploaded, so there is nothing for a server to keep, leak or log. |
| Speed | No round trip to a server, and no queue behind other people's files. |
| Offline use | The page keeps working once it has loaded, even in flight mode. |
| No size cap | The only limit is your browser's memory, not an upload quota. |
How to check any tool's claim
Do not take a privacy claim on trust when you can test it in two minutes. Open your browser's network panel, convert a file and watch what happens. A tool that is truly private shows no upload of your data; only static files such as scripts and styles load. The verification guide walks through the whole check step by step, including what each request in the list is for.
The bottom line
Nobody should have to upload private data just to change a file format. Pick a tool that runs locally, and the conversion costs nothing while the data stays on your own device.
“Every other online converter asks you to upload your data to their server. For unreleased survey or client data, that is a non-starter, which is exactly why this one does not.”
Frequently asked questions
Which formats can I convert this way?
KML, KMZ, Shapefile, GeoJSON, GPX, DXF, CSV and Excel, all handled locally by the same engine, so the data never leaves your device.
Does it cost anything?
No. The conversion runs on your own device, so there is nothing to meter and no reason for a signup, a quota or a paid tier.
What is WebAssembly?
A format browsers can run at close to native speed. It lets a full conversion engine, originally built for desktop software, run inside an ordinary browser tab.
Does browser-based conversion work offline?
Once the page and its engine have loaded, yes. Because the conversion runs locally, you can disconnect and still convert files. That is a side benefit of not using a server.
Is in-browser GIS conversion actually private?
Yes, when the tool processes files locally. You can verify it: open your browser's network panel, convert a file, and confirm that your data is not uploaded. Only static assets should load.