actionpayload

An action payload is the portion of an action object that carries the data required to describe a change in an application's state. In event-driven and state management architectures, actions signal that something happened and provide the details needed to update the state or trigger side effects.

In many frameworks, such as Redux, actions are plain objects with a type field and an optional payload field. The payload typically contains the information necessary for reducers to compute the next state, such as an entity record, identifiers, or result data from a request. Common patterns also support an error flag and a meta object for non-primary information.

Best practices include keeping payloads small and serializable, avoiding direct references to functions or non-serializable objects, and keeping them immutable once created. When dealing with related data, normalization and IDs can reduce duplication. For asynchronous flows, middlewares may dispatch multiple actions, with the initial action carrying enough context to correlate subsequent actions.

The term action payload is widely used interchangeably with payload within action objects; some codebases may concatenate the two words as actionpayload or use a different field name such as data or payload. Regardless of naming, the payload should be clearly defined in a contract or type system to ensure consistent handling by reducers, effects, or handlers.