Trying to do a get through my browser using the account name (impact11) and my key and secret... The URL I am trying is: https://api.constantcontact.com/ws/customers/impact11/contacts. I have also tried impact and IMPACT. I then try to enter my key as the user name and my secret as the password and it fails with a 401. I tried impact, impact11 and IMPACT as user names and the key as the password as well. None of those combos worked.
I am doing this through a browser as a test before I start building more complex functionality.
Am I doing something stupid?
You are not doing anything stupid however the login credentials can be considered confusing.
Your request URI (https://api.constantcontact.com/ws/customers/impact11/contacts) is correct however your username is most likely the cause of the 401 error. Since you are testing in a browser you should be prompted for a User Name and Password.
Your User Name is going to be the combination of your API Key followed by a percent sign (%) and finally your Constant Contact Login name like so:
Your Password is going to be your Constant Contact account password.
Please verify that this is how you are attempting to connect and let us know if you have any other issues.
Support Engineer, Constant Contact