The API key is a code that is used to invoke the Mollie API and identify a customer. Each Mollie account has a unique API key. If you are building a platform or app, then we recommend using Mollie Connect. Mollie Connect uses 'tokens', which allow the Mollie API to be invoked without requiring the Mollie customer’s confidential data, such as their Live API Key.
The Test API Key can only be used to test integration with a Mollie account. This means that when you use the Test API Key, no actual payments are made and you will not be charged for test transactions. The Live API Key is used to make actual payments, for which we also charge certain fees.
TIP! In How can I onboard a customer?, you can read about how to use Mollie Connect to set up a payment for a customer without their Live API Key.
TIP! Never send a Live API Key by e-mail. A Live API Key is unique and should be handled with care.
See also: Can I access a customer’s account?