Validator Web UI
If you'd like to use the web UI, simply visit validator.ampproject.org.
Running your own Web UI
In this directory, run
$ npm install $ go build serve-standalone.go $ ./serve-standalone
Then visit your own instance at http://127.0.0.1:8765/.
If you'd like to run exactly the code that is running at validator.ampproject.org, that's an Appengine app - please refer to the instructions in serve.go.