Flash messages

Flash messages let you send one-time data to users after redirects. Unlike regular props, flash data isn't persisted in browser history - when a user clicks the back button, they won't see old flash messages reappear.

This makes flash perfect for success notifications, error messages, newly created IDs, or any temporary values.

Sending flash messages

Use sails.inertia.flash() in your action:

module.exports = {
  exits: {
    success: {
      responseType: 'redirect'
    }
  },
  fn: async function () {
    await User.updateOne({ id: this.req.session.userId }).set({
      timezone: this.req.body.timezone
    })

    sails.inertia.flash('success', 'Timezone updated successfully')

    return '/settings'
  }
}

Flash with redirects

Flash data survives redirects. Set the flash, redirect, and the data appears on the next page:

module.exports = {
  exits: {
    success: {
      responseType: 'redirect'
    }
  },
  fn: async function () {
    const project = await Project.create(this.req.body).fetch()

    sails.inertia.flash('success', 'Project created!')
    sails.inertia.flash('highlightId', project.id)

    return '/projects'
  }
}

Flash with render

You can also use flash when rendering a page directly:

module.exports = {
  exits: {
    success: {
      responseType: 'inertia'
    }
  },
  fn: async function () {
    const projects = await Project.find()

    sails.inertia.flash('toast', {
      type: 'info',
      message: 'Welcome back!'
    })

    return {
      page: 'projects/index',
      props: { projects }
    }
  }
}

Reading flash messages

Flash data is available on page.props.flash:

Vue

<script setup>
import { usePage } from '@inertiajs/vue3'

const page = usePage()
</script>

<template>
  <div v-if="page.props.flash?.success" class="alert alert-success">
    {{ page.props.flash.success }}
  </div>

  <div v-if="page.props.flash?.error" class="alert alert-error">
    {{ page.props.flash.error }}
  </div>
</template>

React

import { usePage } from '@inertiajs/react'

export default function Layout({ children }) {
  const { flash } = usePage().props

  return (
    <>
      {flash?.success && (
        <div className="alert alert-success">{flash.success}</div>
      )}
      {flash?.error && <div className="alert alert-error">{flash.error}</div>}
      {children}
    </>
  )
}

Svelte

<script>
  import { page } from '@inertiajs/svelte'
</script>

{#if $page.props.flash?.success}
  <div class="alert alert-success">{$page.props.flash.success}</div>
{/if}

{#if $page.props.flash?.error}
  <div class="alert alert-error">{$page.props.flash.error}</div>
{/if}

Global flash event

You can listen for flash data globally using Inertia's event system:

Vue

<script setup>
import { router } from '@inertiajs/vue3'
import { onMounted, onUnmounted } from 'vue'

let removeListener

onMounted(() => {
  removeListener = router.on('flash', (event) => {
    if (event.detail.flash.toast) {
      showToast(event.detail.flash.toast)
    }
  })
})

onUnmounted(() => {
  removeListener?.()
})
</script>

React

import { router } from '@inertiajs/react'
import { useEffect } from 'react'

export default function Layout({ children }) {
  useEffect(() => {
    return router.on('flash', (event) => {
      if (event.detail.flash.toast) {
        showToast(event.detail.flash.toast)
      }
    })
  }, [])

  return children
}

Real-world examples

Toast notifications

// api/controllers/tasks/create.js
module.exports = {
  exits: {
    success: {
      responseType: 'redirect'
    }
  },
  fn: async function () {
    const task = await Task.create(this.req.body).fetch()

    sails.inertia.flash('toast', {
      type: 'success',
      message: 'Task created successfully'
    })

    return `/tasks/${task.id}`
  }
}

Highlight newly created items

// api/controllers/projects/create.js
module.exports = {
  exits: {
    success: {
      responseType: 'redirect'
    }
  },
  fn: async function () {
    const project = await Project.create(this.req.body).fetch()

    sails.inertia.flash('highlightId', project.id)

    return '/projects'
  }
}

<script setup>
import { usePage } from '@inertiajs/vue3'

defineProps({ projects: Array })

const highlightId = usePage().props.flash?.highlightId
</script>

<template>
  <div
    v-for="project in projects"
    :key="project.id"
    :class="{ 'bg-yellow-100': project.id === highlightId }"
  >
    {{ project.name }}
  </div>
</template>

Multiple flash values

sails.inertia.flash('success', 'Project created!')
sails.inertia.flash('highlightId', project.id)
sails.inertia.flash('scrollTo', 'projects-section')

All values are merged into the flash object on the response.

sails.inertia.flash() vs req.flash()

The Boring JavaScript Stack provides two flash mechanisms:

Method	Use case	Available at
sails.inertia.flash()	Inertia apps	page.props.flash
req.flash()	Server-rendered views	Session (via sails-flash)

For Inertia apps, always use sails.inertia.flash(). It:

• Stores flash in the session (survives redirects)
• Automatically includes flash in page.props.flash
• Works without passing req (uses AsyncLocalStorage internally)
• Prevents "phantom" messages when users navigate back

The req.flash() method (from sails-flash) is for traditional server-rendered pages and is not automatically included in Inertia responses.