HTTP 501 Not Implemented — Feature Placeholder & Method Support

When to Return 501

Return 501 for HTTP methods the server doesn't implement at all (rare — most servers support all standard methods). Also used to indicate planned-but-not-yet-built features ('coming soon' API endpoints).

Common Causes

• HTTP method not supported by the server implementation
• Feature announced but not yet built
• Placeholder endpoint in an API design-first workflow

HTTP Response Example

HTTP/1.1 501 Not Implemented
Content-Type: application/json

{"error": "Not Implemented", "message": "This feature is coming soon"}

Code Examples

// Placeholder for planned endpoint
app.post('/ai/generate', (req, res) => {
  res.status(501).json({
    error: 'Not Implemented',
    message: 'AI generation is coming soon. Join the waitlist.',
    waitlistUrl: 'https://example.com/waitlist',
  })
})

// app/api/ai/route.ts — placeholder route
export async function POST() {
  return Response.json(
    { error: 'Not Implemented', message: 'Coming soon' },
    { status: 501 }
  )
}

Related Status Codes