This article explains how to enable developer mode on your Chromebook. Instructions apply to Chromebooks that use a virtualized developer switch. Some Chromebooks, such as the Cr-48 and Samsung Series 5, have physical developer mode switches. Chromium maintains a list of Chromebook models where you can see if your device has a developer switch.

To enable Developer Mode on a Chromebook:

With your Chromebook turned off, boot it into recovery mode by pressing Esc+Refresh while holding the power button.

Wait for the screen that says Chrome OS is missing or damaged. Insert a USB flash drive and press Ctrl+D.