What are signals in Angular and how do you read and update one?

A signal is a value holder that tells Angular when it changes. You create one with signal(initialValue), read it by calling it like a function, and write it with set or update.

import { signal } from '@angular/core'

const count = signal(0)

console.log(count()) // 0
count.set(5)
count.update((n) => n + 1)
console.log(count()) // 6

• set(value) replaces the value.
• update(fn) computes the new value from the old one.
• asReadonly() gives a read-only view you can expose from a service.

In a template you write {{ count() }}. Angular records that the template read the signal, so when count changes it knows exactly which view to refresh. That is called fine-grained reactivity, and it is what makes zoneless change detection possible.

Signals work well for state and derived values with computed.

Always read a signal with parentheses, and update it with set or update.