HTTP 409 Conflict

What is HTTP 409 Conflict?

The 409 (Conflict) status code indicates that the request could not be completed due to a conflict with the current state of the target resource. This is commonly used in version control systems and collaborative editing applications where conflicts arise from concurrent modifications.

Common Use Cases

• Version conflict during resource update
• Editing a resource that has been modified by another user
• Duplicate entry creation attempt

// Laravel - optimistic locking with 409
$post = Post::findOrFail($id);
if ($request->input('version') !== $post->version) {
    return response()->json([
        'error' => 'Version conflict',
        'latest_version' => $post->version,
        'latest_content' => $post->content,
    ], 409);
}