All the Zoho CRM APIs are authenticated with OAuth2 standards, so it is mandatory to register and authenticate your client app with Zoho.

To register:

1. Go to the site: accounts.zoho.com/developerconsole
   
2. Click Add Client ID. 
   
   
   
   
   
3. Enter the Client Name, Client Domain and Authorized Redirect URL.
   
4. Select the Client Type as Web based. 
   
   
   
   
   
5. Click Create.
   
6. Your Client app would have been created and displayed by now.
   
   
   
7. The newly registered app's Client ID and Client Secret can be found by clicking Options → Edit.
   

Note

Options is the three dot icon at the right corner.