WebUSB Access Denied — Browser USB Device Connection and Permission Errors

Fix WebUSB API access denied errors when websites cannot connect to USB devices due to permission issues, driver conflicts, or browser restrictions. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: WebUSB allows websites to communicate with USB devices directly from the browser. It requires HTTPS, user gesture, and explicit user permission via a device chooser dialog. Only Chromium-based browsers support WebUSB — Firefox and Safari do not. Some USB devices are blocked by default: HID keyboards/mice, mass storage, smart cards. OS-level drivers may claim the USB device, preventing WebUSB from accessing it. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: User denied USB device access when the permission dialog appeared. USB device is claimed by an OS driver preventing browser access. Device is in the WebUSB blocklist (HID devices, storage devices are blocked for security). Browser does not support WebUSB (Firefox, Safari, all iOS browsers). Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Click the website's 'Connect' button (user gesture required) and select the device from the chooser dialog. Check if the device needs a driver release: on Linux, may need udev rules; on Windows, may need Zadig. Verify the device is not on the blocklist: HID keyboards, mice, and mass storage are blocked. Use Chrome (or Edge) as the browser — Firefox and Safari do not support WebUSB. For development: test with chrome://usb-internals/ to see connected devices and their descriptors. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Browser Errors collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.