Do We Still Need @track in LWC After Spring ’20?

When Salesforce introduced Lightning Web Components (LWC), developers quickly learned that reactivity was tied to the @track decorator. Before Spring ’20, if you wanted your component to rerender when a property changed, you had to explicitly mark it with @track.

But after the Spring ’20 release, Salesforce simplified the reactivity model. Primitive properties (like strings, numbers, and booleans) and even top-level objects/arrays became reactive by default. This left many developers wondering: Is @track obsolete?

The short answer: not entirely.

When You Still Need @track

The catch lies in nested mutations inside objects or arrays. LWC does not automatically detect changes deep inside unless the property is decorated with @track.

Example:

import { LightningElement, track } from 'lwc';

export default class TrackExample extends LightningElement {

    @track address = {

        city: 'Nagpur',

        country: 'India'

    };

    handleCityChange(event) {

        this.address.city = event.target.value; // Nested mutation

    }

}

Template:

<template>

    <lightning-input label="City" value={address.city} onchange={handleCityChange}></lightning-input>

    <p>City: {address.city}</p>

</template>

With @track: the <p> updates immediately when you type.

Without @track: the <p> won’t update unless you reassign the entire object:

this.address = { ...this.address, city: event.target.value };

Final Thoughts

@track isn’t gone — it’s just less common. Think of it as a tool for special cases rather than a default habit.