Redux v5.0.0: Understanding the AnyAction Deprecation

Anton Ioffe - January 4th 2024 - 10 minutes read

As seasoned architects of the web, our tooling and methodologies are in constant evolution, often testing the robustness of our adaptability and depth of our expertise. In this shifting landscape, Redux v5.0.0 emerges as a beacon of modernized state management, introducing pivotal alterations that warrant a discerning eye. Our journey through its fabric will unravel the deeper motives behind the AnyAction deprecation, the refined type-action dance, and the subtle yet profound enhancements poised to redefine performance. We'll navigate the nuanced architecture, dissect performance optimizations, and arm you with practical wisdom for transitioning to the new order of Redux—all while balancing the essence of legacy with the innovation of the future. Prepare to enrich your development acumen as we disseminate the intricacies and the artfulness imbued in Redux's latest incarnation.

The Shift from AnyAction to UnknownAction in Redux v5.0.0

In Redux v5.0.0, the shift from AnyAction to UnknownAction typifies a strategic move towards enhanced type safety and predictability within state management practices, especially for TypeScript users. In previous versions, AnyAction permitted a permissive attitude toward additional fields on action objects by typing these fields as any. This leniency, while simplifying some use-cases like console.log(action.whatever), provided limited type safety facilitating potential runtime errors. Transitioning to UnknownAction, where all fields except action.type are considered unknown, enforces a stricter contract for actions. Developers must now assert specific TypeScript types through type guards to interact with the action object, bolstering trust in action shape and content.

Middleware type changes further underscore Redux's commitment to solidifying its type system. Previously predicated on certain assumptions about next and action parameters, Redux middleware now acknowledges the dynamic nature of these arguments by typing them as unknown. This necessitates the use of type guards and utilities like isAction to narrow down action types before proceeding with any assumptions. Such rigorous checks lead to a codebase where action creators, such as those provided by Redux Toolkit, offer more precise matching utilities with their .match() method, which isolates types and facilitates improved predictability in state transitions.

Despite these improvements, developers may encounter initial friction adjusting to the stricter typing regimen. No longer can actions be casually passed along middleware chains without explicit type assertions. This discipline helps prevent inadvertent processing or misinterpretation of action objects but assumes a higher baseline of TypeScript fluency. Consequently, while these changes nudge developers towards more robust practices, they may also incur a learning curve where previously common operations now demand additional scrutiny.

Such sweeping type enhancements are not without their compatibility concerns—particularly for legacy codebases. A minority of Redux applications that utilize unusual patterns, such as Symbols for action types, might face issues reconciling their code with UnknownAction. This friction underscores the broader trend within the JavaScript ecosystem: evolving type safety often strains older, more dynamic paradigms. Developers are prompted to refactor towards explicit type assertion patterns to maintain integrity within Redux's enhanced type landscape.

The retrospective examination of AnyAction vis-à-vis UnknownAction provokes thought on the balancing act between ease of development and system robustness. As part of the evolution toward safer TypeScript types in Redux, it begs the question: How do developers value immediacy against reliability in application state management? In embracing UnknownAction, Redux v5.0.0 advocates for thoroughness and intentionality, setting a precedent for future iterations in the rapidly advancing frontier of JavaScript development.

Architectural Benefits and Challenges of Action.type as a String

Enforcing action.type as a string in Redux grants significant architectural advantages, primarily in the realm of serialization. Actions in Redux are meant to be serializable to ensure a predictable state container that can be easily inspected and replayed, a fundamental requirement for powerful developer tools like Redux DevTools. Serialization facilitates state hydration and debugging by providing a readable action history. By mandating that action types must be strings, Redux solidifies a convention that optimizes for tooling compatibility and enhances the overall predictability of Redux applications.

However, the shift poses challenges for some existing codebases. Legacy systems that may have used alternative data types, like Symbols, as action types will face a rude awakening. This can lead to errors that weren't previously present, interrupting workflows and necessitating an immediate response from the development team. The situation highlights a tension between adhering to best practices and maintaining legacy code.

Developers working with codebases affected by this change can adopt several strategies to navigate the transition. A thorough audit of the application's actions is a pivotal first step—identifying areas where non-string action types have been implemented will guide the refactoring process. Subsequent actions include replacing these data types with strings that conform to Redux's new requirement. Throughout this process, unit tests will be invaluable in guarding against regressions.

In situations where refactoring might be challenging due to complex dependencies or tight deadlines, workarounds might be temporarily employed. For example, developers can utilize wrappers or intermediate middleware that translate Symbol-based action types into compliant string-based types. Such solutions should be treated as stop-gap measures and not long-term fixes, given that they can potentially obfuscate the intended clarity that the string requirement aims to bring to Redux architecture.

Despite potential initial difficulties, the architectural benefits of enforcing a string-based action type system are clear. It standardizes the action contract within Redux, leading to applications that are more consistent and less prone to unexpected behavior due to unserializable data. In weighing the trade-offs, the longevity and reliability of a codebase can be significantly improved by embracing this change, serving as an investment in the code’s maintainability and extensibility. It is a measure that asserts the importance of a structured and disciplined approach in modern web development practices.

createStore Deprecation and Modern State Management Practices

The deprecation of createStore in Redux 5.0 is more than a simple retirement of outdated functionality; it signifies a transformative moment in Redux history. Introduced in Redux's formative days, createStore has been instrumental for developers to initialize the store—where the state of the application resides. As the torchbearer of state management practices, its deprecation is indicative of the larger evolution in Redux's architectural philosophy. It is a purposeful stride away from older patterns towards embracing a more robust and scalable approach with configureStore from Redux Toolkit.

configureStore is the heir apparent, not merely replacing createStore but enhancing the state management experience. Redux Toolkit's configureStore engenders a paradigm that simplifies setup and configuration while instilling best practices by default. This fosters modularity, easier maintainability, and a more standardized way of state management across large-scale applications. The modern practice, thus, moves developers towards an ecosystem where Redux logic is consolidated with better defaults and usage patterns, facilitating a cleaner and more maintainable codebase.

The strategy behind depreciating createStore embeds a strong incentive for developers to transition to Redux Toolkit, despite createStore remaining operational with no runtime consequences. This gentle nudge is designed to coax the community into a more homogeneous pattern of Redux usage, one that is characteristically forward-thinking and aligned with modern JavaScript development trends. Consequently, as configureStore supersedes its predecessor, developers inherit a tailored setup that comes equipped with dev-tools and middleware integration, an enhanced developer experience straight out of the box.

However, despite the push towards modernization, the Redux team has accommodated those unready to transition by exporting legacy_createStore. This move ensures that existing applications can sidestep the deprecation visual cues without altering their foundational Redux logic. It presents a stop-gap measure, allowing teams to schedule their refactoring efforts in line with broader developmental timelines while mitigating any immediate technical debt accrued from the transition.

The deprecation is more than a marking of the old; it's a statement on the maturation of state management in JavaScript applications. By advocating for configureStore and Redux Toolkit, the Redux team champions a standardized, more effective state management approach, encouraging best practices such as immutability and asynchronous logic handling. As we witness this historic deprecation unfold, it urges us to reflect on the harmony between maintaining the old and embracing the new, prompting a thought-provoking question: How can we ensure seamless transitions in technology while continuing to innovate and build upon the established foundations?

Streamlining Application Performance with Redux v5.0.0 Build Updates

Redux v5.0.0 introduces a major leap forward in optimizing application performance with its revised approach to module packaging and build outputs. By shifting the primary module format to ECMAScript modules (ESM), Redux offers improved tree-shaking capabilities which can significantly reduce the final bundle size of an application. Smaller bundles translate directly into faster load times, particularly for users on mobile devices or less reliable networks. Furthermore, given that ESM is statically analyzable, build tools like webpack and Rollup can more efficiently determine which pieces of code are actually in use within an application, leading to additional optimization opportunities.

The addition of an exports field in package.json exemplifies Redux's commitment to modern standards, providing clearer entry points for various module resolutions. This change ensures that the appropriate artifact is loaded, depending on the environment, whether it be a Node application or a client-side web application. This flexibility aids in cutting down unnecessary overhead, as the tailored artifact will likely execute faster and consume less memory than a one-size-fits-all bundle. As developers, we must appreciate the immediate implications of these quality-of-life improvements, as they render module resolution precise and mitigate potential performance bottlenecks.

Another aspect impacting performance is Redux v5.0.0's modern build output which utilizes ES2020 features, such as optional chaining and object spread. Although using cutting-edge syntax could raise concerns over compatibility and the need for transpilation steps, the enhancements tend to improve code readability and maintainability. Importantly, for runtime environments that support these features natively, applications can leverage the more efficient native implementations. This can lead to better runtime performance and a reduction in transpilation overhead during the build process.

Noticeably, Redux v5.0.0 discontinues the distribution of Universal Module Definition (UMD) builds, which were once a staple for supporting a variety of module systems. While this may seem like a drawback, in reality, it streamlines the library's consumption by focusing on ESM and CommonJS (CJS) formats, which are predominantly used today. As most modern applications do not require UMD builds, eliminating them can reduce the maintenance complexity and overhead associated with supporting legacy module systems. This forward-thinking approach favors performance optimization and modern workflow practices.

While application performance stands to benefit from these updates, it's crucial to bear in mind the need for a progressive transition. Applications heavily reliant on previous module formats or build outputs will require a carefully managed update strategy to avoid disruption. Although the long-term advantages are clear, the transition phase may pose a temporary increase in complexity as developers adapt to new import patterns and ensure compatibility with existing infrastructure. In a broader sense, Redux v5.0.0 encourages the community to embrace evolving JavaScript standards and, in doing so, harness the substantial performance gains that come with such progress.

Code Migration and Best Practices in Light of Redux v5.0.0 Changes

As Redux v5.0.0 shifts towards better developer experience with improved type safety, a major part of this involves implementing more stringent action type checks within reducers. Below are pertinent code examples and best practices to aid developers in making these transitions seamlessly and efficiently.

When dealing with reducers that handle various action types, your old approach might resemble:

function myReducer(state = initialState, action) {
    switch (action.type) {
        // handlers
            return state;

In your migration, avoid explicitly importing UnknownAction as it's a conceptual construct. Instead, type actions as { type: string } and rest of the fields as unknown, and perform type checking:

function myReducer(state = initialState, action: { type: string } & Record<string, unknown>) {
    if (typeof action.type !== 'string') {
        throw new Error('Action type must be a string.');
    // Perform necessary runtime checks or use helper functions
    // handlers
    return state;

A frequent oversight in migrating to stricter type checking arises from neglecting proper type assertions. Make sure each action passes through a stringent type check to prevent potential runtime type errors.

As createStore is deprecated, the transition to configureStore from Redux Toolkit is the forward path. Use legacy_createStore as an interim step if immediate migration isn't feasible. Here is how you transition:


import { createStore, applyMiddleware } from 'redux';
const store = createStore(rootReducer, applyMiddleware(...middlewares));


import { configureStore } from '@reduxjs/toolkit';
const store = configureStore({
    reducer: rootReducer,
    middleware: (getDefaultMiddleware) => getDefaultMiddleware().concat(...middlewares),

Best practices recommend taking full advantage of Redux Toolkit's default settings. When adding custom middleware, exercise caution not to inadvertently omit or replace any built-in middleware. configureStore also eliminates the manual setup for Redux DevTools, promoting a clean and efficient development workflow.

In the realm of actions, the action.type must invariably be a string. This prerequisite secures serializability and compatibility with Redux middleware and tools. Alterations for action creators should look like this:


const MY_ACTION = Symbol('MY_ACTION');
export function myActionCreator(payload) {
    return { type: MY_ACTION, payload };


export function myActionCreator(payload) {
    return { type: MY_ACTION, payload };

Such adjustments guarantee seamless operation with Redux DevTools and other middleware. Implement these changes throughout your application to mitigate any unintentional functional deviations.

Throughout the refactoring process, assertively question yourself: "Have I confirmed the elimination of AnyAction in favor of strict typings and applied the necessary guards?" and "Are my action types stringently standardized as string literals?" Rigorous examination helps preclude the subtle bugs that can emerge amidst the transition. While deprecated features may not have immediate detrimental effects on your application, proactively adopting these fresh paradigms ensures a sturdier, future-proof codebase in alignment with Redux's evolving direction.


The article discusses the major changes introduced in Redux v5.0.0, focusing on the deprecation of AnyAction, the shift to UnknownAction, enforcing action.type as a string, and the deprecation of createStore. It also highlights the benefits and challenges of these changes, including improved type safety, architectural enhancements, and performance optimizations. The article concludes by encouraging developers to embrace the new features and provides a challenging task of refactoring code to align with Redux's evolving direction. Readers are prompted to examine their code, implement stricter type checking, transition to configureStore, and standardize action types using string literals to ensure a more robust codebase. Task: Review your application's code and make the necessary changes to transition to Redux v5.0.0's stricter type checking, configureStore, and standardized action types using string literals. This will help improve the reliability, maintainability, and performance of your application while aligning with Redux's evolving direction.

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