Is it possible to get user_ID without login?

I’m currently using a website called API Tester to apply these request to the twitch servers, that’s why I didn’t post any code. Did you understand that I’m doing it without the streamer login infos and also without any information of his twitch account apart of the nome of his channel? Cause I don’t know why but I feel that you didn’t.

Any thoughts?

image
In this picture where you see

`-X GET https://api.twitch.tv/kraken/users?login=dallas,dallasnchains`

what this “dallas,dallasnchains” means? Like if I want to check the xxx user_ID do I have to write xxx instead of dallas,dallasnchains ?