>> state passed around as props

Context provides a way to pass data through the component tree without having to pass props down manually at every level. https://reactjs.org/docs/context.html

>> single source of truth

Often, several components need to reflect the same changing data. We recommend lifting the shared state up to their closest common ancestor. https://reactjs.org/docs/lifting-state-up.html

Note that Context is a pretty new API (1), way newer than most state management libraries. Before that it quickly became unmanageable to lift state up and pass props down all the way.

[1] https://github.com/facebook/react/blob/master/CHANGELOG.md#1...

I guess then I have no idea why Redux is so widely used, given now the Context API exists.

Multiple reasons.

First, Redux has been around since 2015 (and won the "Flux Wars" that had been going on for a year before that), whereas the new `createContext` API only came out a few months ago.

Second, Redux provides a lot more guidance around how you're supposed to structure your application. Context only provides a method for making values available to deeply nested components in the tree.

Third, the Redux ecosystem is huge, with addons available for effectively any use case you can think of. [0]

Please see my post "Redux - Not Dead Yet!" [1] and Dave Ceddia's post "Redux vs the React Context API" [2] for more details on how they relate.

[0] https://blog.isquaredsoftware.com/2017/09/presentation-might...

[1] https://blog.isquaredsoftware.com/2018/03/redux-not-dead-yet...

[2] https://daveceddia.com/context-api-vs-redux/

Redux is overused, because of a meme that suggests that the de facto standard React "stack" is React, Redux, and React-Router. That's just a meme (Dan Abramov even wrote a blog post debunking it!) but some memes are hard to fight.

Redux the library is not "state management for react". It's more of a concept that gives you a predictable structure around how state changes over time.

I think what you're thinking of is specifically the `react-redux` library which gave a nice abstraction to the old & clunky React context API. The new context API was released with React 16.3 (which came out March of this year).

The new Context API can't be used in lifecycle methods, which is a bit of a letdown.

the new Context API replaces the `connect()`/`<Provider />` functionality, but not the flux data flow model. Nor does it provide a replacement for the surrounding redux ecosystem - so there's still plenty of benefit to using redux.