Network change test

Hold a connection open, then disturb the network.

A file upload fails with a message like “your network changed” when the connection drops while the request is still open. Chromium calls that net::ERR_NETWORK_CHANGED. This page keeps an upload and a download in flight so you can cause that failure, read it here, and run the same steps in any other browser.

1. Press Start. The counters should keep moving.
2. While they move, switch Wi-Fi, toggle a VPN, or drop the connection for a moment.
3. Both open requests should fail together. The log is what a website can see. The browser download, if you left it checked, shows the browser’s own wording for the same drop.