204 - No Content

What Does No Content Mean?

A 204 response is a "Bodyless Success." While the operation is successful, the intentional absence of a response body often triggers a "SyntaxError: Unexpected end of JSON input" in clients that unconditionally call .json(). In RESTful design, 204 signals that the action was performed (like a deletion) and the client should stay on the current page or state without expecting new data.

Common Causes

• -Unconditional JSON Parsing: The client-side code calls response.json() on a 204 response, which throws an error because the body is empty (0 bytes).
• -Stale UI State: The server returns 204 after a DELETE, but the frontend fails to manually update the local cache, making it appear as if the item still exists.
• -CORS Preflight (OPTIONS): Browsers often send an OPTIONS request before the real request; if the server doesn't return 204 (or 200) with proper headers, the main request is blocked.
• -Cache Inconsistency: A proxy or CDN caches a 204 response incorrectly or fails to invalidate a previous GET response after a successful DELETE/PUT.

How to Fix No Content

1. 1Status Guard: Wrap your parsing logic with if (response.status !== 204) { await response.json(); }.
2. 2Optimistic UI: Immediately remove the deleted record from your state manager (Redux, React Query) once a 204 is received.
3. 3CORS Header Check: Ensure your server returns 204 for OPTIONS requests with the necessary Access-Control-Allow-Methods headers.
4. 4Verify Content-Length: Ensure the server sends Content-Length: 0 or omits it entirely; sending any byte (even a space) violates the 204 spec.

Step-by-Step Diagnosis for No Content

1. 1Open Browser DevTools > Network tab and verify that the "Response" tab for the 204 request is completely empty.
2. 2Check the "Console" for SyntaxError or Unexpected end of input exceptions following a network call.
3. 3Inspect the Content-Type header; a true 204 should ideally not have a Content-Type since there is no content to describe.
4. 4Audit your API Gateway to ensure it isn't injecting an empty object {} into the 204 response, which confuses some clients.

curl -i -X DELETE https://api.errorreference.com/v1/posts/55
# Expected Output:
# HTTP/1.1 204 No Content
# Content-Length: 0
# (No body displayed)

const deleteRecord = async (id) => {
  const res = await fetch(`/api/v1/records/${id}`, { method: 'DELETE' });
  
  // Guard against 204 to avoid JSON SyntaxError
  if (res.status === 204) {
    console.log('Deleted successfully. No body to parse.');
    return null;
  }
  
  return await res.json();
};

How to Verify the Fix

• -Confirm the status code is exactly 204 and no JSON parse errors appear in the console.
• -Perform a subsequent GET request to the resource and verify it returns 404 (if deleted) or reflects the update.
• -Ensure the UI reflects the change (e.g., row disappears) without a page refresh.

How to Prevent Recurrence

• -Standardize API Wrappers: Use a global fetch/axios interceptor that returns null or an empty object for 204 status codes automatically.
• -Prefer 200 for Updates: For PUT operations, consider returning 200 with the full updated object to eliminate "stale state" bugs.
• -Contract Testing: Use tools like Prism to ensure the backend never accidentally sends a body with a 204 status.
• -Pro-tip: For CORS preflight, always use 204 as it is more performant and follows the W3C recommendation for pre-flighted requests.

Related Errors

Decision Support

Official References

• -MDN Web Docs: 204 No Content
• -CORS Preflight Requests & 204
• -RFC 9110 Section 15.3.5 — 204 No Content
• -HTTP Official Documentation