We have implemented an IP restriction after many months fighting manually with misusage far beyond the fair usage. I.e. after a certain credit usage per day the IP will be automatically blocked.
This does not apply to the general Directions API! It applies to the API examples and GraphHopper Maps.
If you hit this limit and use GraphHopper Maps for non-commercial usage you can still make it working: sign up for a developer account, create an API key and then append this API key to GraphHopper Maps URL via
&key=your_api
The good thing about this work is that you, as a customer, can contact us to enable this IP restriction for your account. Useful if you have a public facing application where hiding the API key is not possible.
Note that there are ways to sign requests and avoid exposing the API key, but we did not choose this method (yet) as this would make the client side integration more complicated.