Your photo stays on your device.
This page explains what happens when you use the shutter count checker. Short version: nothing about your photo is sent anywhere.
What happens to your file
When you drop or choose a photo, your browser reads it into memory and a script on the page looks for the camera's maker notes. The result is shown on screen. The file is never uploaded, and the site has no server code that could receive it. When you close or reload the tab, the file is gone from memory.
You can check this yourself. Open your browser's developer tools, switch to the Network tab and read a photo: no request is made. The counter on the page also shows how many network requests happened while your file was being read.
Cookies and tracking
The site sets no cookies, runs no advertising, and loads nothing from third parties. Fonts and scripts are served from this domain.
Hosting
The site is hosted on Cloudflare Pages. Like any web host, Cloudflare processes standard request data such as IP address and browser type in order to deliver pages and protect against abuse. That data concerns the page request, never your photo.
Offline copy
After your first visit, your browser keeps a copy of the page so the checker works without a connection. You can remove it by clearing site data for this domain in your browser settings.
Result cards
When you save a result card, the image is drawn in your browser and downloaded straight to your device. The serial number is masked on the card unless you choose to show it.