When a carrier issues an eSIM, the phone downloads the plan by scanning a QR code that contains an LPA activation string — LPA:1$ followed by the SM-DP+ server address and an activation (matching) code, optionally with a flag that a confirmation code will be required.
This tool builds that string. If your carrier already gave you the full LPA:1$… text, paste it into the top field and the code is generated as-is. Otherwise, enter the SM-DP+ address and activation code separately and, if the plan needs one, tick the confirmation-code box.
The QR code is created entirely in your browser. Scanning it opens the native 'Add eSIM' / 'Add cellular plan' flow on a modern iPhone or Android device — this generator produces the activation code, it does not provision or sell a mobile plan.