No Image Upload: What Local Processing Means and How to Verify It Yourself
Making a pattern from a photo should start with one question: where does this image go? This guide does not ask for trust — the verification at the end requires nothing but switching your network off.
The other side first: where does your image go on an upload-based tool?
"Upload" means the image fully leaves your device and lands on someone else's server. From then on, every copy is out of your control: it may enter access logs, be retained, or be repurposed — none of which you can audit. For photos of your kids or your family, this is not paranoia; it is the default question to ask.
What "local processing" means technically
The conversion engine here — quantization (assigning each cell its nearest color code), cell-by-cell editing, export — is code running inside the browser page. The site has no backend: there is no server listening for incoming images, and no channel through which image data could leave your device.
Which enables the second property: it works offline. The full feature set depends on no server, which is why a single-file offline build — one HTML file, double-click, network off — is possible at all.
Do not take my word for it: verify in three steps
- Get the offline single file from the download page — the page publishes the version, byte size and SHA-256 so you can check the file yourself.
- Disconnect: unplug the cable or switch off Wi-Fi, then double-click the file open.
- Run the whole flow: import an image → convert → edit cells → export the construction sheet and the material list CSV.
If all of that works, the entire chain from conversion to export provably depends on no server — offline, there is nothing to upload to. The online version can be verified the same way: open your browser DevTools Network panel, take one image through the full flow, and watch for any request carrying image data.
When you still need a network
- First load of the online version (fetching the page and code);
- Checking for and fetching updates;
- Downloading the offline single file.
Nothing else requires a connection — conversion, editing, export and project saving all happen on your device.
The trade-off, honestly stated
No cloud also means no cloud sync: moving devices means carrying your project JSON yourself, and clearing browser data discards the auto-recovery records. That is the other side of "images never leave the device" — the data is in your hands, and so is keeping it. If seamless cross-device matters more to you, upload-based tools are genuinely more convenient; if you care where images end up, this is a price worth paying.
For the tool shapes compared, see the tool comparison; for the privacy policy, see the privacy page.