This is a web application wrapper around Salesforce Lightning CLI, using the same npm package but exposing Linter in the browser so as to not require syncing components on the client to run.
You can either submit code blocks for parsing or log into Salesforce to parse all Lightning Components at once. There is also a public endpoint at '/lint-json' which accepts source code in the POST body and returns a JSON list of Lint messages.
There is also a very experimental Chrome Extension which exposes the /lint-json endpoint to the Salesforce Developer Console.
This service is not an official product of Salesforce.com and is offered without support. You can clone/contribute to the code on github.