Mozilla shipped Web Serial API support in Firefox 151, released this week, enabling users to communicate directly with serial-connected hardware — including microcontrollers and development boards — without additional software or complicated setup. The feature lands in the desktop version of Firefox’s Gecko engine and closes a long-standing gap with Chromium-based browsers, which have supported Web Serial for years. As part of the launch, Mozilla partnered with open-source hardware community Adafruit to test and validate browser-based hardware workflows in Firefox: Adafruit’s browser tools, including its WebSerial ESPTool for flashing ESP32 boards, now work directly in Firefox 151. Mozilla describes the collaboration as a signal that different communities — not just mainstream users — should be able to use the web on their own terms.
Web Serial is unlikely to surface in everyday browsing, but it matters significantly for makers, educators, embedded-device developers, and STEM communities that have relied on tools like CircuitPython’s browser-based editor or similar hardware-programming environments that previously required Chrome or Edge. By implementing the API in Gecko, Mozilla extends these workflows to privacy-focused users who prefer Firefox but had been forced to switch browsers for hardware projects. The full engineering writeup covering implementation details is available on Mozilla Hacks.