Web Serial API: Browser Support, Features, Limits

What is the Web Serial API?

The Web Serial API is a JavaScript API on the navigator.serial object that lets a web page open a bidirectional channel with a serial device. The Web Platform Incubator Community Group at the W3C edits the spec, with Reilly Grant at Google as editor. Chrome 89 first shipped the API in March 2021 to let web apps talk to Arduinos, microcontrollers, 3D printers, and other hardware that uses a serial port over USB or Bluetooth.

Which browsers does the Web Serial API support?

Chromium-based desktop browsers ship the Web Serial API by default, while Safari, stable Firefox, Samsung Internet, and most mobile browsers leave it out, so global browser support sits at about 72% as of April 2026.

What are the key features of the Web Serial API?

The Web Serial API gives a web page low-level access to serial input and output streams without a native driver, while keeping the user in control of every device handshake. The main features focus on permissions, stream-based I/O, and event-based device updates.

• navigator.serial.requestPort: Pops a browser device chooser on a click. The user picks a port from a filter of USB vendor and product IDs, and the page only sees the device the user chose.
• navigator.serial.getPorts: Returns ports the user has already approved for the origin. The page never gets a free pass to enumerate hardware.
• SerialPort.open and SerialPort.close: Open and close the port. The open call takes baud rate plus optional data bits, stop bits, parity, flow control, and buffer size.
• SerialPort.readable and SerialPort.writable: Show the port as a ReadableStream and WritableStream, so pages chain TransformStream pipelines to decode text or parse frames.
• SerialPort.setSignals and SerialPort.getSignals: Drive and read DTR, RTS, RI, DSR, and CD control lines for manual hardware flow control.
• connect and disconnect events: Fire on navigator.serial when an approved port is plugged in or unplugged, so pages react to cable changes without polling.
• SerialPort.forget: Revokes the page's permission for that port. Chrome 103 added this method.
• BYOB readers: Chrome 106 added Bring-Your-Own-Buffer reader support, letting pages reuse a Uint8Array across reads to cut allocation pressure.

How do you connect to a serial device with the Web Serial API?

You connect to a serial device by feature-detecting navigator.serial, calling requestPort from a user gesture, opening the port at the right baud rate, and reading from port.readable. Every step has to run on a click or keypress because requestPort requires user activation.

Use the filters argument to narrow the chooser to your hardware. A filter can match usbVendorId and usbProductId, and the browser shows every device that matches at least one filter.

Paste this snippet into the DevTools console of Chrome, Edge, or Opera. Click anywhere on the page once and the device chooser opens.

// Paste this into the DevTools console of Chrome, Edge, or Opera to detect Web Serial and open a port.
if ("serial" in navigator) {
  console.log("Web Serial API is available.");

  document.body.addEventListener("click", async () => {
    const port = await navigator.serial.requestPort();
    await port.open({ baudRate: 9600 });
    console.log("Opened port at 9600 baud:", port.getInfo());

    const reader = port.readable.getReader();
    try {
      const { value, done } = await reader.read();
      if (done) return;
      console.log("Got bytes:", new Uint8Array(value));
    } finally {
      reader.releaseLock();
    }
  }, { once: true });
} else {
  console.log("Web Serial API is not supported in this browser.");
}

If the console prints "Web Serial API is not supported in this browser", you are on Safari, stable Firefox, Samsung Internet, or a mobile browser. Fall back to a native helper app or a Trusted Web Activity for those visitors.

What are the known issues with the Web Serial API?

The Web Serial API has a small browser footprint, and most sharp edges sit at the boundary between the page and the host OS. Painful cases tend to land on Mozilla's harmful position, Apple's opposed stance, mobile gaps, and the user-gesture rule.

• Stable Firefox does not support it: Firefox Nightly 151 added an add-on-gated build in April 2026, but stable Firefox 153 still has no Web Serial. Guide Firefox users to Chrome or Edge.
• WebKit calls the spec harmful: Apple has an opposed standards position citing fingerprinting risk. Safari on macOS, iPadOS, and iOS lack support in every version, so iPad and iPhone visitors need a native app.
• Mobile coverage is thin: Chrome 148 Android shipped in beta in April 2026. Firefox for Android, Samsung Internet, and Opera Mobile do not support it.
• requestPort must run on a user gesture: Chrome throws a SecurityError if you call requestPort from a setTimeout, fetch callback, or page-load handler. Wire it to a click or keypress.
• One tab owns the port: Once a tab opens a port, no other tab can open it until the first tab calls close. Plan UX so two pages do not race onto the same Arduino.
• HTTPS only: navigator.serial is undefined on http:// pages outside of localhost. Ship over HTTPS or use mkcert for local development.
• Bluetooth ports need OS pairing first: The browser only sees Bluetooth serial devices the OS has already paired. Pair the device in Windows, macOS, or ChromeOS settings first.
• BYOB readers and forget arrived late: SerialPort.forget needs Chrome 103+, BYOB readers need Chrome 106+. Older Chromium builds may lack these even though they ship the base API.

In my experience, the trickiest failure is the user-gesture rule paired with React. A useEffect that calls requestPort on mount throws every time, because the browser loses the activation token before the effect runs. Wire requestPort to an onClick handler on a real button and the issue disappears.

Citations

All Web Serial API version numbers and platform notes in this guide come from these primary sources:

• MDN Web Docs - Web Serial API: developer.mozilla.org/en-US/docs/Web/API/Web_Serial_API
• MDN Web Docs - Serial interface: developer.mozilla.org/en-US/docs/Web/API/Serial
• WICG - Web Serial API editor's draft: wicg.github.io/serial
• Chrome for Developers - Read from and write to a serial port: developer.chrome.com/docs/capabilities/serial
• Google Codelabs - Getting started with the Web Serial API: codelabs.developers.google.com/codelabs/web-serial
• Chrome Platform Status - Web Serial API: chromestatus.com/feature/6577673212002304
• Chrome Platform Status - Web Serial API on Android: chromestatus.com/feature/6043992171085824
• Chromium blink-dev - Intent to Ship Web Serial API: groups.google.com/a/chromium.org/g/blink-dev/c/RCtZPCQLLOQ
• Chromium blink-dev - Intent to Ship Web Serial on Android: groups.google.com/a/chromium.org/g/blink-dev/c/HBJ-uYFvkpM
• Mozilla Standards Positions - Serial API: github.com/mozilla/standards-positions/issues/336
• Mozilla Bugzilla - WebSerial API tracker: bugzilla.mozilla.org/show_bug.cgi?id=926940
• WebKit Standards Positions - Web Serial API: github.com/WebKit/standards-positions/issues/199
• Microsoft Learn - Edge SerialAskForUrls policy: learn.microsoft.com/en-us/deployedge/microsoft-edge-browser-policies/serialaskforurls