RemNote does not have its own spell-checker – instead, it uses the spell-checker provided by your web browser (on the web app) or operating system (on the desktop app or mobile app). The language used by the spell-checker is thus determined by the settings in your browser or operating system.

If you're using RemNote in your browser, you can usually tell the browser what languages you know and which you want it to spell-check. The exact details depend on the browser.

In Google Chrome and other Chromium-based browsers, you can find the option under “Languages” in the settings. (You can get here quickly by going to chrome://settings/languages.)

In System Settings on your Mac, go to Keyboard > Text Input > Input Sources > Edit. Select an appropriate language, or Automatic by Language to have macOS guess the language you're currently typing in.

Note that, unlike on the browser or the Windows/Linux desktop app, you can only have a single manually selected language (this is a macOS limitation, not a RemNote one). If you write in multiple languages, Automatic by Language is likely the best selection here.

In Settings > Editor, open the Spell Checker Languages drop-down and select the languages you'd like to use.

If you're unable to set your browser or operating system language to match the language you're taking notes in, or you otherwise don't want to spell-check your notes, you can disable the spell-checker entirely using Settings > Editor > Enable Spellcheck.