Most of these come up once, get fixed in ten seconds, and never bother you again. Here's the list, roughly in the order people hit them.

Nothing happens when I type

The Translate button will be greyed out, and you'll need to sign in. While you're signed out the automatic translate quietly does nothing rather than showing an error, which is a bit unhelpful of it. Sign in and it picks straight up with the English you already typed.

If you clicked explain while signed out you may see a message blaming our end. Ignore the wording: signing in is the fix.

The Upload button is greyed out

Either you're in Firefox or Safari, which can't talk to USB, or the board you picked is one of the compile-only ones. Chrome, Edge and Opera can flash. See compiling and flashing for the board table.

My Arduino isn't in the port list

That list is the browser's, not ours, so if the board isn't there your computer can't see it either. In order of likelihood: the cable is a charge-only one with no data wires (very common, and worth testing with a known-good cable), the board isn't plugged in properly, or the USB-serial driver isn't installed. Clone boards with a CH340 chip usually need that driver on Windows and older macOS.

"Could not open the port: … is something else using it?"

Something else has the board. Usually the desktop Arduino IDE's serial monitor, another tab with English open, or a terminal app. Close the other one and try again.

It won't be our own Serial Monitor, since we close that for you during an upload and reopen it afterwards.

"Could not sync to the bootloader after 8 tries"

The sketch compiled, but the board didn't answer when we knocked. Three usual causes:

It's a Nano clone. Switch the board dropdown to "Arduino Nano (old bootloader / clone)". This is the fix nine times out of ten.
Wrong port. Click the ✕ to forget the board and pair it again.
Something grabbed the port mid-upload. Close other serial apps.

The Serial Monitor is showing gibberish

The baud rate doesn't match. The dropdown has to be the same number as the Serial.begin(...) in your sketch, which is usually 9600. Change it and the monitor reconnects on its own.

The plot is empty

The Plot tab reads the same stream as the Serial Monitor, so the monitor has to be open. If it is open and you're still getting nothing, check your sketch is printing actual numbers: lines with no digits in them are ignored on purpose so status messages don't spike the graph.

"Fatal error: something.h: No such file or directory"

The sketch asked for a library the compiler doesn't have. The console lists every library that is available right underneath, so rephrase your English around one of those. Which libraries you can use has the full list.

The translation stopped halfway

Very long programs can run past the limit. Shorten the English, or split the job into a couple of smaller programs. A translation that hasn't finished after two minutes gives up by itself and tells you so.

"HTTP 429"

You've translated a lot in a short time and hit the fair-use limit, which is 60 a minute. Wait a moment and carry on. Nothing is broken and nothing is charged.

No line numbers, no click-to-link highlighting

Your network is blocking the CDNs the editor loads from, which is common on school and office networks. English still works: you can write, translate, Verify and Upload. What you lose is the fancy editor, the ribbon and explain. The hosts to allow-list are listed with the privacy notes.

My work disappeared

If you were signed out, work lives only in that browser, so clearing site data, a private window, or a different computer will lose it. Signed in, your most recent project comes back when you sign in again.

If you keep several projects going, export each one to a .english file. The projects menu is per-browser and shouldn't be relied on to sync.

Still stuck?

Tell us what you typed and what came back, and we'll have a look. We're a small team in Sydney and the same people who built this read the mail.

Troubleshooting English