WebUsbProvider

WebUsbProvider implements SerialProvider using the WebUSB API as a polyfill for the native Web Serial API.

When to use

• Android Chrome — Web Serial is not available; WebUSB is the only way to talk to USB serial adapters.
• Desktop testing — Force the WebUSB code path to verify behaviour before deploying to Android.
• Custom USB devices — Devices not exposed via Web Serial (e.g. custom vendor-class USB).

Supported protocols

Protocol	USB class	Notes
CDC ACM	Class 0x02	Standard Arduino, ST-LINK
CP210x / CH340	Vendor-specific	Common USB-UART bridges
Raw bulk	Any class	Generic bulk-transfer devices

Import

import { WebUsbProvider } from "webserial-core";

Constructor

new WebUsbProvider(options?: SerialPolyfillOptions)

Option	Type	Default	Description
usbControlInterfaceClass	number	10	USB interface class for control transfers
usbTransferInterfaceClass	number	10	USB interface class for bulk transfers

For devices using vendor-class interfaces (CP210x, CH340):

new WebUsbProvider({
  usbControlInterfaceClass: 255,
  usbTransferInterfaceClass: 255,
});

Usage

import { AbstractSerialDevice, delimiter } from "webserial-core";
import { WebUsbProvider } from "webserial-core";

AbstractSerialDevice.setProvider(
  new WebUsbProvider({
    usbControlInterfaceClass: 255,
    usbTransferInterfaceClass: 255,
  }),
);

class MyDevice extends AbstractSerialDevice<string> {
  constructor() {
    super({
      baudRate: 9600,
      parser: delimiter("\n"),
      filters: [{ usbVendorId: 0x10c4, usbProductId: 0xea60 }], // CP2102
    });
  }

  protected async handshake(): Promise<boolean> {
    return true;
  }
}

const device = new MyDevice();
await device.connect(); // Opens WebUSB device picker

Per-instance usage

Pass provider (and optionally polyfillOptions) in the constructor options to bind WebUsbProvider to a single device instance without touching the global provider.

import { AbstractSerialDevice, delimiter, WebUsbProvider } from "webserial-core";

class MyUsbDevice extends AbstractSerialDevice<string> {
  constructor() {
    super({
      baudRate: 9600,
      parser: delimiter("\n"),
      filters: [{ usbVendorId: 0x10c4, usbProductId: 0xea60 }],
      provider: new WebUsbProvider({
        usbControlInterfaceClass: 255,
        usbTransferInterfaceClass: 255,
      }),
    });
  }

  protected async handshake(): Promise<boolean> {
    return true;
  }
}

const device = new MyUsbDevice();
await device.connect();

Alternatively, pass polyfillOptions separately and let the library forward them to whichever provider resolves for that instance:

class MyUsbDevice extends AbstractSerialDevice<string> {
  constructor() {
    super({
      baudRate: 9600,
      parser: delimiter("\n"),
      provider: new WebUsbProvider(),
      polyfillOptions: { usbControlInterfaceClass: 255 },
    });
  }

  protected async handshake(): Promise<boolean> {
    return true;
  }
}

Browser support

Requires a Chromium-based browser with WebUSB enabled. Not available in Firefox or Safari. Requires HTTPS or localhost.