If you find your Chromebook lags even when you're not doing anything online (e.g. when you're using the calculator or watching a locally-saved video), it could be a sign that you need to update your chromebook.
Google is constantly releasing new versions of the operating system. They will automatically install themselves whenever you restart your computer, but if you're the kind of person who leaves your computer running 24/7, you could be a few updates behind.
Check if there's a small arrow in the bottom right-hand corner of the display. If there is, you have updates to install. You will need to Shutdown your chromebook and re-start
