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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.

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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.

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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

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Callback Method

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

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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"
    ]
  }
}

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Status Code Description

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code
integer
required
Callback status code indicating task processing result:
Status CodeDescription
200Success - Image generation completed
500Server Error - Image generation failed or other internal error
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msg
string
required
Status message providing detailed status description
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data.taskId
string
required
Task ID, consistent with the taskId returned when you submitted the task
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data.promptJson
string
required
JSON string containing the original request parameters, useful for tracking generation request details
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data.resultUrls
array
required
Array of result URLs for generated images/videos, contains accessible download links on success

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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');
});

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Best Practices

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Callback URL Configuration Recommendations

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

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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

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Troubleshooting

If you do not receive callback notifications, please check the following:
  • 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
  • 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
  • Confirm that the received POST request body is in JSON format
  • Check that Content-Type is application/json
  • Verify that JSON parsing is correct
  • 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

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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.