Automatically back up your data to your own Google Drive as a JSON file. Important: Google sign-in only works when this app is hosted at a real web address (https://...) — it will not work when the file is opened directly by double-clicking (a file:// address). You'll also need to create a free Google Cloud OAuth Client ID for your hosted site and paste it below. If you're not sure how, use the "Download Backup (JSON)" button on the left instead — it works everywhere, no setup needed.

Connect this to keep all your computers/devices showing the same live data automatically — sales, inventory, and returns entered on one device appear on the others within a second or two. This is different from Google Drive Backup above, which is just a manual periodic snapshot. Uses Firebase (Google's free real-time database — no credit card needed, generous free tier). Every device must use the exact same Firebase config and Shop ID below to share data.