Midjourney Image Generation Callbacks

When you submit an image generation task to the Midjourney API, you can use the callBackUrl parameter to set a callback URL. The system will automatically push the results to your specified address when the task is completed.

Callback Mechanism Overview

The callback mechanism eliminates the need to poll the API for task status. The system will proactively push task completion results to your server.

Callback Timing

The system will send callback notifications in the following situations:

Midjourney image generation task completed successfully
Midjourney image generation task failed
Errors occurred during task processing

Callback Method

HTTP Method: POST
Content Type: application/json
Timeout Setting: 15 seconds

Callback Request Format

When the task is completed, the system will send a POST request to your callBackUrl in the following format:

{
  "code": 200,
  "msg": "success",
  "data": {
    "taskId": "mj_task_12345",
    "promptJson": "{\"prompt\":\"a beautiful landscape\",\"model\":\"midjourney\"}",
    "resultUrls": [
      "https://example.com/mj_result1.png",
      "https://example.com/mj_result2.png",
      "https://example.com/mj_result3.png",
      "https://example.com/mj_result4.png"
    ]
  }
}

Status Code Description

code

integer

required

Callback status code indicating task processing result:

Status Code	Description
200	Success - Image generation completed
500	Server Error - Image generation failed or other internal error

msg

string

required

Status message providing detailed status description

data.taskId

string

required

Task ID, consistent with the taskId returned when you submitted the task

data.promptJson

string

required

JSON string containing the original request parameters, useful for tracking generation request details

data.resultUrls

array

required

Array of result URLs for generated images/videos, contains accessible download links on success

Callback Reception Examples

Here are example codes for receiving callbacks in popular programming languages:

Node.js
Python
PHP

const express = require('express');
const app = express();

app.use(express.json());

app.post('/mj-image-callback', (req, res) => {
  const { code, msg, data } = req.body;
  
  console.log('Received Midjourney image generation callback:', {
    taskId: data.taskId,
    status: code,
    message: msg
  });
  
  if (code === 200) {
    // Task completed successfully
    console.log('Midjourney image generation completed');
    
    // Parse original request parameters
    try {
      const promptData = JSON.parse(data.promptJson);
      console.log('Original prompt:', promptData.prompt);
    } catch (e) {
      console.log('Failed to parse promptJson:', e);
    }
    
    // Process generated images
    const resultUrls = data.resultUrls || [];
    console.log(`Generated ${resultUrls.length} images:`);
    
    resultUrls.forEach((url, index) => {
      console.log(`Image ${index + 1}: ${url}`);
    });
    
    // Download and save images
    // Add image download logic here
    
  } else {
    // Task failed
    console.log('Midjourney image generation failed:', msg);
    
    // Handle failure cases...
  }
  
  // Return 200 status code to confirm callback received
  res.status(200).json({ status: 'received' });
});

app.listen(3000, () => {
  console.log('Callback server running on port 3000');
});

from flask import Flask, request, jsonify
import requests
import json

app = Flask(__name__)

@app.route('/mj-image-callback', methods=['POST'])
def handle_callback():
    data = request.json
    
    code = data.get('code')
    msg = data.get('msg')
    callback_data = data.get('data', {})
    task_id = callback_data.get('taskId')
    prompt_json = callback_data.get('promptJson', '{}')
    result_urls = callback_data.get('resultUrls', [])
    
    print(f"Received Midjourney image generation callback: {task_id}, status: {code}, message: {msg}")
    
    if code == 200:
        # Task completed successfully
        print("Midjourney image generation completed")
        
        # Parse original request parameters
        try:
            prompt_data = json.loads(prompt_json)
            print(f"Original prompt: {prompt_data.get('prompt', '')}")
        except json.JSONDecodeError as e:
            print(f"Failed to parse promptJson: {e}")
        
        # Process generated images
        print(f"Generated {len(result_urls)} images:")
        
        for i, url in enumerate(result_urls):
            print(f"Image {i + 1}: {url}")
            
            # Download image example
            try:
                response = requests.get(url)
                if response.status_code == 200:
                    filename = f"mj_image_{task_id}_{i + 1}.png"
                    with open(filename, "wb") as f:
                        f.write(response.content)
                    print(f"Image saved as {filename}")
            except Exception as e:
                print(f"Image download failed: {e}")
                
    else:
        # Task failed
        print(f"Midjourney image generation failed: {msg}")
        
        # Handle failure cases...
    
    # Return 200 status code to confirm callback received
    return jsonify({'status': 'received'}), 200

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=3000)

<?php
header('Content-Type: application/json');

// Get POST data
$input = file_get_contents('php://input');
$data = json_decode($input, true);

$code = $data['code'] ?? null;
$msg = $data['msg'] ?? '';
$callbackData = $data['data'] ?? [];
$taskId = $callbackData['taskId'] ?? '';
$promptJson = $callbackData['promptJson'] ?? '{}';
$resultUrls = $callbackData['resultUrls'] ?? [];

error_log("Received Midjourney image generation callback: $taskId, status: $code, message: $msg");

if ($code === 200) {
    // Task completed successfully
    error_log("Midjourney image generation completed");
    
    // Parse original request parameters
    $promptData = json_decode($promptJson, true);
    if ($promptData) {
        error_log("Original prompt: " . ($promptData['prompt'] ?? ''));
    } else {
        error_log("Failed to parse promptJson");
    }
    
    // Process generated images
    error_log("Generated " . count($resultUrls) . " images:");
    
    foreach ($resultUrls as $index => $url) {
        error_log("Image " . ($index + 1) . ": $url");
        
        // Download image example
        try {
            $imageContent = file_get_contents($url);
            if ($imageContent !== false) {
                $filename = "mj_image_{$taskId}_" . ($index + 1) . ".png";
                file_put_contents($filename, $imageContent);
                error_log("Image saved as $filename");
            }
        } catch (Exception $e) {
            error_log("Image download failed: " . $e->getMessage());
        }
    }
    
} else {
    // Task failed
    error_log("Midjourney image generation failed: $msg");
    
    // Handle failure cases...
}

// Return 200 status code to confirm callback received
http_response_code(200);
echo json_encode(['status' => 'received']);
?>

Best Practices

Callback URL Configuration Recommendations

Use HTTPS: Ensure your callback URL uses HTTPS protocol for secure data transmission
Verify Source: Verify the legitimacy of the request source in callback processing
Idempotent Processing: The same taskId may receive multiple callbacks, ensure processing logic is idempotent
Quick Response: Callback processing should return a 200 status code as quickly as possible to avoid timeout
Asynchronous Processing: Complex business logic should be processed asynchronously to avoid blocking callback response
Batch Processing: Midjourney typically generates multiple images, recommend batch downloading and processing

Important Reminders

Callback URL must be a publicly accessible address
Server must respond within 15 seconds, otherwise it will be considered a timeout
If 3 consecutive retries fail, the system will stop sending callbacks
Please ensure the stability of callback processing logic to avoid callback failures due to exceptions
Midjourney generated image URLs may have time limits, recommend downloading and saving promptly
Pay attention to processing the promptJson field, which contains useful original request information

Troubleshooting

If you do not receive callback notifications, please check the following:

Network Connection Issues

Confirm that the callback URL is accessible from the public network
Check firewall settings to ensure inbound requests are not blocked
Verify that domain name resolution is correct

Server Response Issues

Ensure the server returns HTTP 200 status code within 15 seconds
Check server logs for error messages
Verify that the interface path and HTTP method are correct

Content Format Issues

Confirm that the received POST request body is in JSON format
Check that Content-Type is application/json
Verify that JSON parsing is correct

Image Processing Issues

Confirm that image URLs are accessible
Check image download permissions and network connections
Verify image save paths and permissions
Note that Midjourney may generate multiple images requiring batch processing

Alternative Solution

If you cannot use the callback mechanism, you can also use polling:

Poll Query Results

Use the get Midjourney task details endpoint to regularly query task status. We recommend querying every 30 seconds.

Midjourney API

Common API

​Callback Mechanism Overview

​Callback Timing

​Callback Method

​Callback Request Format

​Status Code Description

​Callback Reception Examples

​Best Practices

​Callback URL Configuration Recommendations

​Important Reminders

​Troubleshooting

​Alternative Solution

Poll Query Results

Callback Mechanism Overview

Callback Timing

Callback Method

Callback Request Format

Status Code Description

Callback Reception Examples

Best Practices

Callback URL Configuration Recommendations

Important Reminders

Troubleshooting

Alternative Solution