Using REST with my key id worked, curl https://api.polygon.io/v1/last_quote/stocks/AAPL?key_id=XXX worked {"status":"success","symbol":"AAPL","last":{"askprice":189.22,"asksize":1,"askexchange":19,"bidprice":189.21,"bidsize":2,"bidexchange":19,"timestamp":1557862846384}}

however using webSocket end authentication msg {"action":"auth","params":"XXX"} to wss://socket.polygon.io/stocks, I received authentication error {"ev":"status","status":"error","message":"authentication failed"}]

For anyone finding this old issue through a search, the websocket interface for Polygon is now supported, and you can use one of our many SDKs to access it.

Note that if you are attempting to access it directly, the URI for our customers using Alpaca KEY_ID is wss://alpaca.socket.polygon.io/stocks