Day 1
Before you connect

Get your board talking to this page

A few quick things to check first — this avoids most connection problems.

How it connects
this computerUSBchipyour Arduino
1
Plug your Arduino Uno into this computer via USB — the same cable you use to upload sketches.
2
Open this page in Chrome or Edge on desktop. Web Serial doesn't work in Safari, Firefox, or on mobile.
3
Make sure your sketch is uploaded and running, printing lines like {"left":562,"right":578,"angle":90} at 9600 baud.
4
Close the Arduino IDE's Serial Monitor — only one program can read the port at a time.
5
Click Connect to Arduino below, then pick your board from the browser's port list.
One connection at a time. If the page seems stuck after connecting, refresh and reconnect instead of stacking connect attempts.