Hypermedia is the REST architectural constraint (often called HATEOAS — Hypermedia As The Engine Of Application State) in which API responses include links and controls that tell a client what it can do next. Rather than hardcoding URLs and workflows, a hypermedia client follows links and forms provided by the server, letting the API evolve and guide the application through its states. It is expressed through concrete media types such as HAL, Siren, Collection+JSON, JSON:API, and JSON-LD.
Hypermedia
Hypermedia is the part of REST that most APIs quietly skip — and the part I have spent the most time championing. In a hypermedia API, responses do not just carry data; they carry links and controls that tell the client what actions are available next. This is what the acronym HATEOAS (Hypermedia As The Engine Of Application State) is pointing at.
- Links as the engine of state - The server tells the client where it can go and what it can do, instead of the client hardcoding URLs and flows.
- Evolvability - Because clients follow links, servers can change structure and workflow with far less breakage.
- Concrete media types - Hypermedia shows up in the wild through formats like HAL, Siren, Collection+JSON, JSON:API, and JSON-LD.
- Newly relevant for agents - As AI agents consume APIs, self-describing, link-driven responses become a practical way to let a machine discover what it can do next.
I have written dozens of posts documenting hypermedia in the wild across real APIs, arguing that its promise was never about the perfect client — and that in an agentic world, hypermedia’s links-and-controls model finally has an audience that benefits from it.
Referenced on the API Evangelist blog
Where this standard shows up across sixteen years of my writing at apievangelist.com — how it fits into API design, governance, and the agentic turn.
TVMaze Uses HAL For Their API Media Type
2018-07-16
Resources
Related Rules
Response Links Info
API responses needs to include links for discoverability, enabling clients to navigate related resources using HATEOAS patterns.
Response Links Required
API responses must include links for discoverability, enabling clients to navigate related resources using HATEOAS patterns.
