The activeCollab API (or Application Programming Interface), is a set of methods that enables activeCollab to comunicate with another application. These methods are then used to read, edit and write data back in activeCollab.
You can find more information about activeCollab's API on your Profile page under the API Settings tab.
To establish a connection with another application you will need your API URL and API Key, both of which are available from the API Settings page.
One particular application that uses the activeCollab API is activeCollab Timer, in this application you need to input your API Key and API URL in order to create an account that will then send data from the application (in this case the amount of time spent on a specific task) back into activeCollab.
If you wish to find out more about activeCollab's API you can find a series of articles containing detailed descriptions of all supported methods in our Developer's Guide.