HTTP 404 Not Found — Causes, Fix & Custom Error Pages

When to Return 404

Use 404 when a resource with the given identifier doesn't exist. For resources that existed but were permanently removed, consider 410 Gone. For protected resources where you don't want to reveal existence, return 404 instead of 403.

Common Causes

• Incorrect URL or typo in the path
• Resource deleted or never existed
• Outdated bookmark or link
• Wrong API version or endpoint path
• Case-sensitive URL mismatch

HTTP Response Example

HTTP/1.1 404 Not Found
Content-Type: application/json

{"error": "Not Found", "message": "User 123 does not exist"}

Code Examples

app.get('/users/:id', async (req, res) => {
  const user = await db.users.findById(req.params.id)
  if (!user) {
    return res.status(404).json({
      error: 'Not Found',
      message: `User ${req.params.id} does not exist`,
    })
  }
  res.json(user)
})

// Catch-all 404 handler (must be last)
app.use((req, res) => res.status(404).json({ error: 'Not Found' }))

// app/users/[id]/page.tsx
import { notFound } from 'next/navigation'

export default async function UserPage({ params }) {
  const { id } = await params
  const user = await db.users.findById(id)
  if (!user) notFound() // renders app/not-found.tsx with 404 status
  return <UserProfile user={user} />
}

Related Status Codes