HMAC(Hash-based message authentication code) is a message authentication code that uses a cryptographic hash function such as SHA-256, SHA-512 and a secret key known as a cryptographic key. HMAC is more secure than any other authentication codes as it contains Hashing as well as MAC.
Below is a free online tool that can be used to generate HMAC authentication code. We can generate hmac-sha256 as well as hmac-sha512 code with it.
First, enter the plain-text and the cryptographic key to generate the code. Then, you can use select the hash function you want to apply for hashing. The default is SHA-256. Then you can submit your request by clicking on the compute hash button to generate the HMAC authentication code for you.
By default, the output is in plain-text format but you also have an option to get the output in Base64 format. Below is a screenshot of the usage: