HTTP 415 Unsupported Media Type — Content-Type Validation

When to Return 415

Return 415 when a client sends a Content-Type you don't support (e.g., text/plain when you only accept application/json), or when you receive multipart/form-data but only handle JSON.

Common Causes

• Sending text/plain to an endpoint that requires application/json
• Submitting an image in the wrong format (e.g., BMP when only JPEG/PNG are accepted)
• Missing Content-Type header on a POST request
• Wrong charset encoding (text/html instead of text/html; charset=utf-8)

HTTP Response Example

HTTP/1.1 415 Unsupported Media Type
Content-Type: application/json

{"error": "Unsupported Media Type", "message": "Expected application/json"}

Code Examples

const requireJson = (req, res, next) => {
  if (!req.is('application/json')) {
    return res.status(415).json({
      error: 'Unsupported Media Type',
      message: 'Content-Type must be application/json',
      accepted: ['application/json'],
    })
  }
  next()
}

app.post('/users', requireJson, createUser)

export async function POST(request: Request) {
  const contentType = request.headers.get('content-type') ?? ''
  if (!contentType.includes('application/json')) {
    return Response.json(
      { error: 'Unsupported Media Type', message: 'Expected application/json' },
      { status: 415, headers: { Accept: 'application/json' } }
    )
  }
  const body = await request.json()
  // proceed
}

Related Status Codes