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Documentation Index

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Tauri v2 uses a capability and permission system to control which IPC commands your frontend JavaScript can call into the Rust backend. Every plugin command is blocked by default — you must explicitly grant access in a capabilities file before your app can list printers, send print jobs, or run test prints. This model follows the principle of least privilege: your app only exposes the exact surface area it needs, reducing the attack vector for malicious web content running inside the WebView.

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Adding Permissions to Your Capabilities File

Capabilities are declared in JSON files inside src-tauri/capabilities/. The default file is src-tauri/capabilities/default.json. Add the thermal-printer permission identifiers you need to the permissions array: 
{
  "permissions": [
    "core:default",
    "thermal-printer:allow-list-thermal-printers",
    "thermal-printer:allow-print-thermal-printer",
    "thermal-printer:allow-test-thermal-printer"
  ]
}
You can also use the shorthand "thermal-printer:default" to enable all four permissions at once — allow-ping, allow-print-thermal-printer, allow-list-thermal-printers, and allow-test-thermal-printer — as defined in the plugin’s default permission set.

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Default Permission Set

The plugin ships a pre-composed default set that grants access to every command exposed by the plugin. It is defined in permissions/default.toml: 
[default]
description = "Default permissions for the plugin"
permissions = [
  "allow-ping",
  "allow-print-thermal-printer",
  "allow-list-thermal-printers",
  "allow-test-thermal-printer",
]
Reference it in your capability file as "thermal-printer:default" to enable everything at once.

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Permission Reference

The table below lists every permission identifier provided by the plugin. Each command has a matching allow-* entry (grants access) and a deny-* entry (blocks access).
Deny permissions take precedence over allow permissions. If the same command is covered by both an allow-* and a deny-* rule — whether through direct listing or through a composed permission set — the denial always wins and the command will be blocked.
IdentifierDescription
thermal-printer:allow-list-thermal-printersEnables the list_thermal_printers command — returns all printers visible to the host OS.
thermal-printer:deny-list-thermal-printersDenies the list_thermal_printers command.
thermal-printer:allow-print-thermal-printerEnables the print_thermal_printer command — sends a PrintJobRequest to a printer.
thermal-printer:deny-print-thermal-printerDenies the print_thermal_printer command.
thermal-printer:allow-test-thermal-printerEnables the test_thermal_printer command — sends a diagnostic test print.
thermal-printer:deny-test-thermal-printerDenies the test_thermal_printer command.
thermal-printer:allow-pingEnables the internal ping command used by the plugin’s health check.
thermal-printer:deny-pingDenies the ping command.

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Android Bluetooth Permissions

On Android the plugin communicates with thermal printers over Bluetooth SPP (Serial Port Profile). The following Android permissions are declared directly in the Kotlin plugin manifest and are requested automatically at runtime — you do not need to add anything to your Tauri capability files for them:
  • BLUETOOTH
  • BLUETOOTH_ADMIN
  • BLUETOOTH_SCAN
  • BLUETOOTH_CONNECT
  • ACCESS_FINE_LOCATION
The user will see a system dialog asking to grant Bluetooth access the first time your app attempts to list or connect to a printer. Make sure the target device has already paired the printer in the Android Bluetooth settings, and pass the printer’s MAC address (e.g. "AA:BB:CC:DD:EE:FF") as the printer field in your PrintJobRequest.

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Principle of Least Privilege

Only add the permissions your app actually uses. For example, if your app only prints and never needs to list printers programmatically, omit thermal-printer:allow-list-thermal-printers from your capabilities file. This minimises the commands available to any script running inside the WebView.
A minimal capabilities file that only allows printing looks like this: 
{
  "$schema": "../gen/schemas/desktop-schema.json",
  "identifier": "default",
  "description": "enables the default permissions",
  "windows": ["main"],
  "permissions": [
    "core:default",
    "thermal-printer:allow-print-thermal-printer"
  ]
}
The capabilities file lives at: 
src-tauri/capabilities/default.json

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