Building a Production-Ready Todo App in Angular with Signals and LocalStorage

Angular Signals quietly changed the way serious Angular applications should be written.

Not because RxJS is obsolete. Not because NgRx is wrong. But because local UI state no longer needs industrial machinery.

In this article, we’ll build a production-grade Todo application using modern Angular primitives:

• Signals for state management
• Computed signals for derived state
• Effects for persistence
• LocalStorage as a lightweight data layer
• Dark mode, filters, and inline editing
• Clean, testable, scalable architecture

This is not a beginner tutorial. This is about designing state correctly in modern Angular.

Why Signals Change Everything

For years, Angular developers defaulted to one of two extremes:

• Overusing BehaviorSubject and subscriptions
• Or introducing NgRx for even small applications

Both approaches work — but both introduce accidental complexity for problems that are fundamentally synchronous and UI-driven.