MobX vs Zustand (2026)

TL;DR

Zustand for most React projects; MobX for complex domain logic or OOP teams. Zustand (~10M weekly downloads) is simpler, more idiomatic for functional React, and has a gentler learning curve. MobX (~3.5M downloads) uses observable reactivity that auto-tracks dependencies — powerful for complex state but adds conceptual overhead. Teams migrating from Angular or with OOP backgrounds often prefer MobX.

Key Takeaways

• Zustand: ~10M weekly downloads — MobX: ~3.5M (npm, March 2026)
• MobX uses observables — mutations are tracked automatically via Proxy
• Zustand is explicit — you call set() to update state
• MobX-React-Lite is tiny — ~1.5KB for the React bindings
• MobX scales to complex domains — class-based stores map to domain models

---

Reactivity Model: Observable vs Explicit

The fundamental difference between MobX and Zustand is how they propagate state changes to your components. MobX wraps your state in Observables using JavaScript Proxies. Any component that reads an observable while rendering automatically subscribes to that observable's changes — no explicit subscription required. Zustand requires you to explicitly select the pieces of state your component cares about using a selector function.

Neither approach is objectively better. The tradeoff is between automatic granular reactivity (MobX) and transparent, predictable subscriptions (Zustand). MobX's automatic tracking is powerful: a component that accesses cart.total in its render output automatically re-renders only when total changes, even if other cart properties change. But the magic can also be a source of confusion — a component that accesses too many observable properties may re-render more often than expected, and debugging why a component is (or isn't) re-rendering requires understanding MobX's dependency tracking.

Zustand's explicit selectors are more verbose but easier to reason about. If a component subscribes to state.items and state.discount, it re-renders when either of those changes. You can read the selector and immediately understand what will trigger a re-render. This predictability is especially valuable in large teams where multiple developers work on the same components.

// MobX — observables track dependencies automatically
import { makeAutoObservable } from 'mobx';
import { observer } from 'mobx-react-lite';

class CartStore {
  items: Array<{ id: string; name: string; price: number; quantity: number }> = [];
  discount = 0;

  constructor() {
    makeAutoObservable(this);
  }

  addItem(item: { id: string; name: string; price: number }) {
    const existing = this.items.find(i => i.id === item.id);
    if (existing) {
      existing.quantity++;
    } else {
      this.items.push({ ...item, quantity: 1 });
    }
  }

  removeItem(id: string) {
    this.items = this.items.filter(i => i.id !== id);
  }

  setDiscount(pct: number) {
    this.discount = pct;
  }

  // Computed values — auto-cached, only recompute when dependencies change
  get subtotal() {
    return this.items.reduce((sum, i) => sum + i.price * i.quantity, 0);
  }

  get total() {
    return this.subtotal * (1 - this.discount / 100);
  }

  get itemCount() {
    return this.items.reduce((sum, i) => sum + i.quantity, 0);
  }
}

const cartStore = new CartStore();

// Components must be wrapped in observer() to react to store changes
const CartSummary = observer(() => (
  <div>
    <span>{cartStore.itemCount} items</span>
    <span>${cartStore.total.toFixed(2)}</span>
  </div>
));
// This component auto-subscribes to: items, discount, total, itemCount
// It re-renders ONLY when those observables change

// Zustand — explicit state selection
import { create } from 'zustand';

interface CartState {
  items: Array<{ id: string; name: string; price: number; quantity: number }>;
  discount: number;
  addItem: (item: { id: string; name: string; price: number }) => void;
  removeItem: (id: string) => void;
  setDiscount: (pct: number) => void;
}

const useCartStore = create<CartState>((set, get) => ({
  items: [],
  discount: 0,
  addItem: (item) => set((state) => {
    const existing = state.items.find(i => i.id === item.id);
    if (existing) {
      return {
        items: state.items.map(i =>
          i.id === item.id ? { ...i, quantity: i.quantity + 1 } : i
        ),
      };
    }
    return { items: [...state.items, { ...item, quantity: 1 }] };
  }),
  removeItem: (id) => set((state) => ({
    items: state.items.filter(i => i.id !== id),
  })),
  setDiscount: (pct) => set({ discount: pct }),
}));

// Computed values via selectors — not memoized by default, use useMemo if expensive
const CartSummary = () => {
  const items = useCartStore(state => state.items);
  const discount = useCartStore(state => state.discount);

  const itemCount = items.reduce((sum, i) => sum + i.quantity, 0);
  const subtotal = items.reduce((sum, i) => sum + i.price * i.quantity, 0);
  const total = subtotal * (1 - discount / 100);

  return (
    <div>
      <span>{itemCount} items</span>
      <span>${total.toFixed(2)}</span>
    </div>
  );
};

MobX's computed values (.total, .itemCount) are automatically memoized and only recompute when their observed dependencies change. In Zustand, you compute derived values inline or with useMemo — there's no built-in memoized computed layer.

---

TypeScript and Class-Based Design

MobX works best with class-based stores using makeAutoObservable. This produces a natural object-oriented pattern that maps well to domain models: a UserStore class has user state, authentication methods, and computed views of that state all in one place. Teams coming from Angular, Java, or C# find this pattern immediately familiar. Angular's services are essentially the same pattern — a class with state and methods — and MobX brings that ergonomic into React without requiring Angular's dependency injection system. Java and C# developers who are learning React often find MobX's class-based model dramatically easier to work with than React's functional paradigm, because they can continue writing in patterns they already know.

// MobX — class-based store, natural OOP domain model
import { makeAutoObservable, runInAction } from 'mobx';

class UserStore {
  user: User | null = null;
  loading = false;
  error: string | null = null;

  constructor() {
    makeAutoObservable(this);
  }

  async login(email: string, password: string) {
    this.loading = true;
    this.error = null;
    try {
      const user = await authApi.login(email, password);
      runInAction(() => {          // Required for async mutations
        this.user = user;
        this.loading = false;
      });
    } catch (err) {
      runInAction(() => {
        this.error = (err as Error).message;
        this.loading = false;
      });
    }
  }

  logout() {
    this.user = null;
  }

  get isLoggedIn() { return this.user !== null; }
  get displayName() { return this.user?.name ?? 'Guest'; }
  get isAdmin() { return this.user?.role === 'admin'; }
}

export const userStore = new UserStore();

// Zustand — functional store, idiomatic for React hooks
import { create } from 'zustand';

interface UserState {
  user: User | null;
  loading: boolean;
  error: string | null;
  login: (email: string, password: string) => Promise<void>;
  logout: () => void;
}

const useUserStore = create<UserState>((set) => ({
  user: null,
  loading: false,
  error: null,
  login: async (email, password) => {
    set({ loading: true, error: null });
    try {
      const user = await authApi.login(email, password);
      set({ user, loading: false });
    } catch (err) {
      set({ error: (err as Error).message, loading: false });
    }
  },
  logout: () => set({ user: null }),
}));

The Zustand version is arguably more concise for simple cases. MobX's runInAction() requirement for async mutations is a common point of confusion for newcomers — it exists because MobX uses batching to prevent intermediate state from triggering renders, and async operations require you to explicitly mark where mutations happen. Once understood, it becomes routine, but it's one of the rough edges of the MobX learning curve.

For large domain models with many computed values and cross-store dependencies, MobX's class-based approach scales more cleanly — it's essentially standard OOP with reactive glue. You can have a CartStore that depends on a InventoryStore, with computed values on CartStore that observe both — and MobX handles the dependency graph automatically. Building equivalent behavior in Zustand requires explicit subscriptions or combining selectors from multiple stores, which becomes verbose at scale.

---

React Integration

Zustand integrates with React through standard hooks with no special setup. Import the store hook and use it — no provider, no HOC, no configuration. Components subscribe to only the state slice returned by the selector.

MobX requires one extra step: components that read observable state must be wrapped in observer(). This is where many developers trip up initially — forget observer() and the component won't re-render when the store changes.

// MobX — observer() is required for reactivity
import { observer } from 'mobx-react-lite';

// Without observer() — component never re-renders on store changes
const BrokenHeader = () => (
  <nav>{userStore.displayName}</nav>   // Won't update ❌
);

// With observer() — automatic subscription to accessed observables
const WorkingHeader = observer(() => (
  <nav>{userStore.displayName}</nav>   // Auto-updates when user.name changes ✓
));

// Local observable state via useLocalObservable
const SearchBar = observer(() => {
  const local = useLocalObservable(() => ({
    query: '',
    setQuery(q: string) { this.query = q; },
  }));

  return (
    <input
      value={local.query}
      onChange={e => local.setQuery(e.target.value)}
    />
  );
});

// Zustand — no wrapper needed, works with standard hooks
// No provider, no observer(), no HOC
const Header = () => {
  const displayName = useUserStore(state =>
    state.user?.name ?? 'Guest'
  );
  return <nav>{displayName}</nav>;
};

// Context-free — works anywhere in the component tree
const AdminBadge = () => {
  const isAdmin = useUserStore(state => state.user?.role === 'admin');
  return isAdmin ? <span>Admin</span> : null;
};

Both integrate cleanly in practice, but Zustand's no-setup approach reduces the onboarding friction significantly. The observer() requirement in MobX is a small tax, but it enables MobX's key superpower: surgical re-rendering. An observer() component only re-renders when the specific observables it accesses change — nothing more, nothing less.

This granularity becomes important in applications with large lists or complex UI where unnecessary re-renders cause visible performance degradation. A Zustand component that selects an entire array will re-render whenever any item in that array changes. A MobX observer() component that accesses userStore.users[userId].name will only re-render when that specific user's name changes. For most applications this distinction doesn't matter — React's reconciliation handles unnecessary re-renders efficiently. For high-density UIs (data tables, dashboards with many live-updating values), MobX's precision is a real advantage.

Zustand also ships with middleware beyond DevTools. The persist middleware stores state to localStorage (or any storage adapter) and rehydrates on page load — essential for persisting cart contents or user preferences across sessions. The immer middleware lets you write mutating code (same mental model as MobX) and handles the immutable update mechanics automatically. These middlewares are composable and well-tested, covering common patterns that you'd otherwise implement manually.

---

DevTools and Debugging

Both libraries have DevTools support, though the experience differs in setup complexity.

MobX has its own DevTools available as a browser extension and via mobx-react-devtools. You can inspect observable state trees, track computed value dependencies, and trace which observables triggered a re-render.

Zustand integrates with Redux DevTools via its devtools middleware, which many developers already have installed:

// Zustand — Redux DevTools integration
import { create } from 'zustand';
import { devtools } from 'zustand/middleware';

const useCartStore = create<CartState>()(
  devtools(
    (set) => ({
      items: [],
      addItem: (item) => set(
        (state) => ({ items: [...state.items, item] }),
        false,           // Replace? (false = merge)
        'cart/addItem'   // Action name shown in DevTools
      ),
    }),
    { name: 'CartStore' }
  )
);

Zustand's Redux DevTools integration shows action names, state diffs, and time-travel debugging. This setup is two lines of middleware and works immediately with any existing Redux DevTools installation. MobX's DevTools setup is slightly more involved but offers deeper observable dependency tracking.

---

Package Health

Metric	Zustand	MobX
Weekly downloads	~10M	~3.5M
GitHub stars	~49K	~27K
Last release	Active	Active
TypeScript	Built-in	Built-in
Maintained	Yes (pmndrs)	Yes (Michel Weststrate)
Bundle size	~1KB	~16KB core + ~1.5KB React bindings

Zustand's download lead is significant and reflects its position as the default state management library for functional React development in 2026. Both are actively maintained — Zustand by the Poimandres open source collective (also behind Jotai, React Spring, and Drei), MobX by Michel Weststrate who created it. Weststrate is also the author of Immer (used internally by Redux Toolkit), demonstrating deep expertise in JavaScript reactivity systems.

MobX's smaller bundle size relative to its feature set is worth noting: ~16KB for the core MobX library and ~1.5KB for the React bindings is extremely lean for a framework that provides full observable state management, computed values, reactions, and automatic dependency tracking. The total MobX + mobx-react-lite bundle is comparable in size to Zustand for the functionality it provides.

---

When to Choose

Choose Zustand when:

• Starting a new React project with functional components and hooks
• Team is comfortable with functional programming patterns
• You want simple, explicit state updates with minimal mental overhead
• Most typical SaaS state: auth, UI flags, cart, form state
• You want Redux DevTools integration with minimal configuration

Choose MobX when:

• Team comes from Angular, Java, or C# background and prefers OOP
• Complex domain logic maps naturally to class-based stores with many computed values
• Fine-grained reactivity matters — many components observing many fields, surgical re-renders needed
• You prefer automatic dependency tracking over manual selectors
• Large state trees where computed memoization provides meaningful performance gains

---

The bottom line: for a typical React SaaS application — auth state, user preferences, shopping cart, UI flags — Zustand is the right default. It has fewer concepts, better documentation for beginners, and integrates naturally with the functional React patterns that most teams use in 2026. MobX earns its place in complex domain-driven applications where the observable pattern maps cleanly to the business model and the team's OOP background makes class-based stores the natural fit.

For current download trends and release history, see the MobX vs Zustand comparison page. If you're evaluating alternatives in the same space, the Zustand vs Jotai 2026 article covers the atom-based approach. The Zustand package page tracks release cadence and ecosystem growth.