API

curl -X GET "https://api.cloudflare.com/client/v4/accounts/{ACCOUNT_ID}/workers/services/{WORKER_NAME}" \
  -H "Authorization: Bearer <TOKEN>" \
  -H "Content-Type: application/json"

type PlacementStatus = 
  | undefined  // Not yet analyzed
  | 'SUCCESS'  // Successfully optimized
  | 'INSUFFICIENT_INVOCATIONS'  // Not enough traffic
  | 'UNSUPPORTED_APPLICATION';  // Made Worker slower (reverted)

// Remote placement (Smart Placement routed request)
"cf-placement: remote-LHR"  // Routed to London

// Local placement (default edge routing)  
"cf-placement: local-EWR"   // Stayed at Newark edge

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const placementHeader = request.headers.get('cf-placement');
    
    if (placementHeader?.startsWith('remote-')) {
      const location = placementHeader.split('-')[1];
      console.log(`Smart Placement routed to ${location}`);
    } else if (placementHeader?.startsWith('local-')) {
      const location = placementHeader.split('-')[1];
      console.log(`Running at edge location ${location}`);
    }
    
    return new Response('OK');
  }
} satisfies ExportedHandler<Env>;

# Tail Worker logs
wrangler tail your-worker-name

# Tail with filters
wrangler tail your-worker-name --status error
wrangler tail your-worker-name --header cf-placement

# Check placement status via API
curl -H "Authorization: Bearer $TOKEN" \
  https://api.cloudflare.com/client/v4/accounts/$ACCOUNT_ID/workers/services/$WORKER_NAME \
  | jq .result.placement_status

// Placement status returned by API (field may be absent)
type PlacementStatus = 
  | 'SUCCESS'
  | 'INSUFFICIENT_INVOCATIONS'
  | 'UNSUPPORTED_APPLICATION'
  | undefined;

// Placement configuration in wrangler.jsonc
type PlacementMode = 'smart' | 'off';

interface PlacementConfig {
  mode: PlacementMode;
  // Legacy fields (deprecated/removed):
  // hint?: string;  // REMOVED - no longer supported
}

// Explicit placement (separate feature from Smart Placement)
interface ExplicitPlacementConfig {
  region?: string;
  host?: string;
  hostname?: string;
  // Cannot combine with mode field
}

// Worker metadata from API response
interface WorkerMetadata {
  placement?: PlacementConfig | ExplicitPlacementConfig;
  placement_status?: PlacementStatus;
}

// Service Binding for backend Worker
interface Env {
  BACKEND_SERVICE: Fetcher;  // Service Binding to backend Worker
  DATABASE: D1Database;
}

// Example Worker with Service Binding
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Forward to backend Worker with Smart Placement enabled
    const response = await env.BACKEND_SERVICE.fetch(request);
    return response;
  }
} satisfies ExportedHandler<Env>;