Go to the GOV.UK Prototype Kit site to download the latest version and read the documentation.
The prototype kit provides a simple way to make interactive prototypes that look like pages on GOV.UK. These prototypes can be used to show ideas to people you work with, and to do user research.
Read the project principles.
If you publish your prototypes online, they must be protected by a username and password. This is to prevent members of the public finding prototypes and thinking they are real services.
You must protect user privacy at all times, even when using prototypes. Prototypes made with the kit look like GOV.UK, but do not have the same security provisions. Always make sure you are handling user data appropriately.
We have two Slack channels for the Prototype kit. You'll need a government email address to join them.