As a web developer, you have various choices regarding API authentication. This guide aims to provide you with a high-level overview of the six most used schemes. Inside, you will find a cheatsheet to help you choose.
TLS mutual authentication doubles down on HTTPS. Using this scheme your clients' identity is proved by presenting certificates and proving ownership of a private key. This is a very potent tool and also a tradeoff.
HTTP signature schemes provide integrity and authenticity on the application layer. Using them increase security but also incurs complexity.
Lots of modern web application utilize bearer tokens. They are ideal for backend integration, but can also be used on the frontend.
Cookies are the de-facto authentication between browser and server. For a good reason, they can provide full-blown session management with low complexity.