Dynamic components let you switch between components at runtime using the built-in <component> element with the :is prop. By default, Vue destroys the old component and creates a new one on each switch. <KeepAlive> changes that behavior by caching instances in memory.

Dynamic components

<script setup>
import { ref, shallowRef } from 'vue'
import TabHome from './TabHome.vue'
import TabSettings from './TabSettings.vue'
import TabProfile from './TabProfile.vue'

const tabs = { TabHome, TabSettings, TabProfile }
const currentTab = shallowRef(TabHome)
</script>

<template>
  <button v-for="(comp, name) in tabs" :key="name" @click="currentTab = comp">
    {{ name }}
  </button>

  <!-- Destroyed and recreated on every switch -->
  <component :is="currentTab" />
</template>

Without KeepAlive, any local state in TabSettings (form inputs, scroll position, expanded sections) resets every time you switch away and back.

Adding KeepAlive

Wrap <component> in <KeepAlive> to cache instances instead of destroying them.

<template>
  <KeepAlive>
    <component :is="currentTab" />
  </KeepAlive>
</template>

Now switching tabs preserves each component's full state.

Controlling what gets cached

Use include, exclude, and max to limit caching.

<template>
  <!-- Only cache these two -->
  <KeepAlive include="TabHome,TabSettings">
    <component :is="currentTab" />
  </KeepAlive>

  <!-- Cache everything except this one -->
  <KeepAlive exclude="TabProfile">
    <component :is="currentTab" />
  </KeepAlive>

  <!-- Cache at most 5 instances (LRU eviction) -->
  <KeepAlive :max="5">
    <component :is="currentTab" />
  </KeepAlive>
</template>

include and exclude match the component's name. Set it explicitly with defineOptions:

<script setup>
defineOptions({ name: 'TabSettings' })
</script>

Lifecycle hooks for cached components

Cached components don't fire onMounted/onUnmounted on switch. Use onActivated and onDeactivated instead.

<script setup>
import { onActivated, onDeactivated } from 'vue'

onActivated(() => {
  // Component became visible again, refresh data if needed
  refreshData()
})

onDeactivated(() => {
  // Component hidden but still alive, pause background work
  pausePolling()
})
</script>

Full lifecycle for a cached component:

onMounted → onActivated → (user switches away) → onDeactivated
         → (user switches back) → onActivated → ...
         → (cache evicted or parent destroyed) → onUnmounted

KeepAlive with Vue Router

<template>
  <router-view v-slot="{ Component, route }">
    <KeepAlive>
      <component :is="Component" :key="route.fullPath" />
    </KeepAlive>
  </router-view>
</template>

Using route.fullPath as the key means /users/1 and /users/2 are cached separately.

When NOT to use KeepAlive

Scenario	Why
Memory-heavy components (maps, large tables)	Cached instances stay in memory
Sensitive data (auth forms, payment flows)	Data should be cleared on exit
Components with background timers you can't pause	They keep running while hidden
Pages where users expect fresh results	Stale cached data confuses users