Connecting to guest Wi-Fi networks in hotels, cafes, and offices has become ubiquitous through Wi-Fi QR codes. However, standard smartphone cameras often parse these codes silently without displaying the raw credentials, and many mobile scanning apps aggressively monetize or harvest network SSIDs and WPA keys by routing camera frames through cloud servers.

In this deep-dive, we examine how client-side WebAssembly (Wasm) and HTML5 Canvas APIs enable instant, zero-latency, and 100% private QR and barcode decoding directly within any modern web browser.

The Security Flaw with Cloud-Based QR Scanners

Traditional online scanning tools often require uploading an image to a remote backend server for computer vision processing. This introduces several distinct privacy hazards:

Network Credentials Leakage: A Wi-Fi QR code contains the full string in the format WIFI:T:WPA;S:MyNetwork;P:SuperSecretPassword;H:false;; .…