What is shared state?

Shared state is common state that is shared between multiple components.

---

#What this means:

When two or more components use the same data, and a change in one place must be reflected in another. For example:

• The cart on the product page and the icon in the header
• An authentication flag in the navbar and in the profile
• A shared filter that affects multiple lists

---

#Where shared state lives:

• In a service (most often)
• In an RxJS stream (BehaviorSubject, signal)
• In a store (NgRx, NGXS, and so on)

---

#Why it matters:

Without shared state, components easily "drift apart": one shows stale data, another shows fresh data. Shared state guarantees that every part of the application "looks at the same place".

---

Conclusion: Shared state is like a single point of truth for multiple participants. Change it in one place, and it changes everywhere.