Code and access token in a weird format

I’m trying to implement OAuth flow in my app. 
First, I get the code back in a weird format, eg: 7ZkE3gpTrD_NG86d8zvTCOFtuNNXD-PuA

I don’t know what those underscores are. When I make a subsequent request, I get a properly formatted response, with access_token and refresh_token, but again, access_token seems way too long and in an invalid format:

eyJnbGciOiJIUpUxZiJ9.eyJhdWQiOiJodHRcczovL29hdXRoLnpvb20udXMiLCJhY2NvdW50SWQiOiJWY21vWDBxMlFVV3BrTE1vWGs0LUxnIiwidmVyIjoiMS4xIiwibmJmIjoxNTMxODIzNTc5LCJjbGllbnRJZCI6ImZ6eWEzWndYUnY2SGRuck83MEFNZmciLCJpc3MiOiJ1cm46em9vbTpjb25uZWN0OmNsaWVudGlkOmZ6eWEzWndYUnY2SGRuck83MEFNZmciLCJlbnYiOltudWxsXSwiZXhwIjoxNTMxODI3MTc5LCJ0b2tlblR5cGUiOiJhY2Nlc3NfdG9rZW4iLCJpYXQiOjE1MzE4MjM1NzksInVzZXJJZCI6Ik5HOTZkOGZ2VENPWnR1Qk5YRC1QdUEiLCJqdGkiOiI0MjA1OGNkYi0xYWYzLTRjOGItYjFkNy1lZjI3ODJkNTAwNTYifQ.hGHI0VD3oUsivCESOT4aEfX3Ok0MhuZtH7N8JXs9iLoFv85p6QLQD2q4jA05Oe1FG0vZbsMIeQIw-0xexKtF1g

Any ideas what this is and where it’s coming from?

Hi Maja, 

The code and access token are designed to have dashes and underscores, along with a long access token for security reasons. Does your access token work?

Thanks