I have downloaded GraphHopper and needed area of OSM map. After starting graphhopper I go to http://localhost:8989 and see "API key not valid for this application (Referrer URL)".
How I can disable API key check on self-hosted GraphHopper?
I'm assuming that you get this message for and in the map tiles. You should not get it for localhost, but if you host it on your server with your own domain then you'll get it.
Note that GraphHopper is only about routing and does not visualize the map. We use an external service Omniscale for the maps and you can sign up there to get a free map tile key yourself. Or just switch to the many free services with the button in the top right corner (or switch to it permanently). Or host a map tile server on your own.