Documentation for our new v4 API can be found here: v4 API Documentation

Authenticating on the v4 Documentation 

1. Scroll down to the green /login endpoint and click Try It Out.
2. Replace string with your API key. If you have a user-supported key, enter your subscriber PIN in the PIN section. If not, remove the PIN section.
3. Click Submit, and it will return a token. Copy that token.
4. Scroll back up to the top of the page, and select the Authorize box in the top right.
5. Paste your token into the box and click Authorize
   

Please also see our list of known bugs and issues for more information. If there are additional issues that you're experiencing, please submit a ticket to the Developers help topic.

Older v3 API documentation can be found here.