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Mozilla Brings Web Serial Workflows to Firefox, Collaborates With Adafruit (mozilla.org) 43

The Web Serial API lets websites write to (and read from) serial devices using JavaScript, including USB and Bluetooth devices with virtual serial ports. And this week's Firefox 151 release introduced support for the Web Serial API on desktop.

"Most folks won't use this API," acknowledges Mozilla's blog, "but for our community of builders and tinkerers, it unlocks the ability to use Firefox to communicate directly with compatible hardware devices like microcontrollers, development boards, and other serial-connected devices..." With Firefox's browser engine, Gecko, now supporting Web Serial, users can now connect, code, configure, and control compatible hardware directly from the browser in many workflows, often without additional software or complicated setup...

As part of this week's launch, Adafruit, one of the internet's most beloved open-source hardware communities, is collaborating with us to test and validate what browser-based hardware development can look like in Firefox with Web Serial support... With Web Serial support in Firefox 151, Adafruit's browser-based hardware workflows now work directly in Firefox as well, with no additional software or complicated setup required for many projects. We invite you to give it a try...

We want the web to be open, flexible, and shaped by the diversity of people building on it. If you're wiring up your first board, experimenting with hardware projects, or dusting off an old electronics kit, give Adafruit and Web Serial in Firefox a try. Build something amazing. Make something useful. Tell us what works. Tell us what breaks. Most of all, make it your own.

Mozilla's "Hacks" blog demonstrates with an Adafruit ESP32-S2 based board "where messages sent from web code can be directly displayed on the device over Web Serial."

And Mozilla engineer Alex Franchuk even built a handheld device that changes a web page's CSS properties.

Mozilla Brings Web Serial Workflows to Firefox, Collaborates With Adafruit

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  • This Is Great News (Score:5, Interesting)

    by crunchy_one ( 1047426 ) on Sunday May 24, 2026 @04:15PM (#66158780)
    Now I can dump Chrome in the trash where it belongs. Web Serial support was the sole reason I've kept it on my machines.Thank you Mozilla, thank you Adafruit!
    • All this time I've bee doing it wrong. Using minicom to browse the internet.

    • by caseih ( 160668 )

      Yes I'm happy to see this as well. It's funny to read the comments here on slashdot. It's readily apparent those who know what this API is for and those that don't! Indeed the Web Serial API makes it fast and easy for beginners to get into Arduino using the web-based Arduino cloud IDE, or even just to install Circuit Python or MicroPython to a microcontroller. Also good for interacting with and setting up IOT devices.

      • In my case I was using Chrome to run configurators for drones.

        And what I was thinking is that it would be nice to have a web-based version of CHIRP.

  • This is great. (Score:4, Insightful)

    by Kamineko ( 851857 ) on Sunday May 24, 2026 @04:25PM (#66158790)

    I do love it when malware advert javascripts can upload random new firmware updates into my mouse and keyboard turning them into stealth keyloggers. This is great.

    This feels like when Flash sandbox breaks became a thing, but worse. At least in those days we got smooth fullscreen vector animations and games to enjoy. I'd rather Flash had just been bloody fixed instead of browsers themselves becoming Shit Flash But Holy Cow It Runs Worse And Gets Worse.

    • by znrt ( 2424692 )

      I do love it when malware advert javascripts can upload random new firmware updates into my mouse and keyboard turning them into stealth keyloggers. This is great.

      so you're using a serial mouse in 2026 to browse porn? that's so "cool"!!

      • It's called Universal SERIAL Bus, btw.

    • You'd get a popup to choose the port and grant permissions.

      Have you ever flashed a Meshtastic or ESPHome device or updated firmware on a radio transceiver?

      That's what they're talking about here.

    • by caseih ( 160668 )

      How did this get modded insightful? Kameniko uses rs232 keyboards? Obviously they don't have any clue what web serial is used for.

    • by tlhIngan ( 30335 )

      I do love it when malware advert javascripts can upload random new firmware updates into my mouse and keyboard turning them into stealth keyloggers. This is great.

      This feels like when Flash sandbox breaks became a thing, but worse. At least in those days we got smooth fullscreen vector animations and games to enjoy. I'd rather Flash had just been bloody fixed instead of browsers themselves becoming Shit Flash But Holy Cow It Runs Worse And Gets Worse.

      You'd have to really be terrible to let it happen. First,

  • It had better be disabled by default.

    • It requires permissions just like accessing a camera or microphone. Stop being paranoid.
      • It's still a new code base and one that can access hardware so it's understandable that people would be nervous.

        At the very least it should probably be something that has to be enabled in settings. And maybe it does I haven't looked into it. There are too many examples of security vulnerabilities that can bypass permissions. That's what the grandparents is worried about
  • by LordHighExecutioner ( 4245243 ) on Sunday May 24, 2026 @04:52PM (#66158816)

    ...a way to freeze Internet explorer was by inserting a < img src=lpt1: > tag in the html code.

  • by mmiscool ( 2434450 ) on Sunday May 24, 2026 @05:34PM (#66158852) Homepage
    Sites like https://serialterminal.com/ [serialterminal.com] will work in firefox. It was like pulling teeth to finally get brave to support this also. Now the only one left is safari.
  • Because it's the first thing that comes to my mind: much easier support for client-side digital document signatures using token certificates (like thumbdrive or smartcard devices) plugged in the client machine.
    This has been a pain in both my previous and current job. Both provided SaaS products that worked with digitally-signed XML files. But when the client opted for using tokens/smartcards, we had no other choice than make the client install a client-side software to do it locally and send it back to the

  • was "uh-oh". I really hope I'm wrong but I don't want Chrome to gain access to my hardware. Nope. How to disable this thing? As far as making a device to change css, okay Adafruit is cool but did Chrome need to blow open a whole new manifold of attack surfaces for this otherwise fun project? (again hope I'm wrong but tldr so will wait for someone else to figure it out)

    • Just like chrome, you have to specifically enable it. And then select the device you want to access every single time you access it. You're fine. Nothing to see here unless it's a feature you actively already use.

    • by caseih ( 160668 )

      Chrome has had web serial for at least five years. Not really sure what you're talking about with adafruit and css.

  • Jaw on the floor how this makes it sound like some amazing new things from Mozilla and Adafruit. This was in Chrome over 5 years ago and has been use by countless projects along the way. Great to see it finally get in Firefox but, uh, how about "after objecting this provably useful API for years, we finally implemented it" as a more accurate summary.

  • I receively bought an xtelink 4 e-reader and was able to flash the thing with custom firmware directly from the browser. This safer IMO that launching some random flash software which might decide to anything when it starts.

    I could see this also being very useful for people wanting to flash embedded devices from cloud based software. But it could also be used to drive braille readers, point of sale terminals and anything else that works over serial.

  • This was one of the few things I still used Chrome for. Just hope there are not stupid restrictions like not being able to access the serial API from local files.

  • This is not as bad as I had originally thought. Apparently the Web Serial API only works with devices with a CDC-ACM (Communications Device Class - Abstract Control Model) interface and it's highly unlikely that most consumer keyboards or mice support that. However, there's also WebHID and WebUSB which may be able to interface directly with consumer keyboards or mice, but I don't believe any browser other than Chromium-based ones support that.
    • by ceoyoyo ( 59147 )

      The consumer stuff is generally all USB and the ship sailed a long time ago on the browser having access to that.

      Browser access to virtual com ports is more an issue for things like industrial control. Somebody is defininitely going to make their SCADA system web based for the "easy updates" and find out.

      Still, the ship sailed on that one a long time ago with Chrome too, and more generally a long, long time ago when Google convinced us all it's a great idea for your operating system to download software off

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