Objective: Ensure that the seed and keys generate exclusively in your browser, on your device, and do not transmit to any other device. The same applies when using the lookup feature.
Method for Any Device
Generate keys on your device by disconnecting from the network or using airplane mode.
Optional Method
Save the wallet HTML file and then use it with the network disconnected.
Linux or Mac curl "https://bitpurz.com/wallet/index.php" -o bitpurz.html
Windows Invoke-WebRequest -Uri "https://bitpurz.com/wallet/index.php" -OutFile "bitpurz.html" -UseBasicParsing