Start with Midjourney API

Understand the core concept

The MidJourney API simulates Discord button interactions. Unlike typical REST APIs, it works as a state machine where each operation returns new buttons for the next step.

The 4 core APIs

API	Purpose	When to Use
`POST /mj/submit/imagine`	Text-to-image generation	Starting point for all workflows
`GET /mj/task/\{id\}/fetch`	Query task status & get buttons	After every submit (poll until done)
`POST /mj/submit/action`	Click a button (upscale, vary, zoom, etc.)	When you want to operate on an image
`POST /mj/submit/modal`	Submit additional input	Only when status is `MODAL`

Complete workflow diagram

┌─────────────────────────────────────────────────────────────────────────────┐
│                         MIDJOURNEY API WORKFLOW                             │
└─────────────────────────────────────────────────────────────────────────────┘

  ┌──────────────────┐
  │  POST /submit/   │  ← Step 1: Submit prompt, get task_id
  │     imagine      │
  └────────┬─────────┘
           │ Returns: { "result": "task_id_1" }
           ▼
  ┌──────────────────┐
  │ GET /task/{id}/  │  ← Step 2: Poll until status = "SUCCESS"
  │      fetch       │
  └────────┬─────────┘
           │ Returns: imageUrl + buttons[] (U1,U2,U3,U4,V1,V2,V3,V4,🔄)
           ▼
  ┌──────────────────┐
  │  POST /submit/   │  ← Step 3: Click a button using customId
  │     action       │
  └────────┬─────────┘
           │ Returns: { "result": "task_id_2" }
           ▼
  ┌──────────────────┐
  │ GET /task/{id}/  │  ← Step 4: Poll the new task
  │      fetch       │
  └────────┬─────────┘
           │
           ├─── status = "SUCCESS" → Done! Get imageUrl
           │
           └─── status = "MODAL" → Need additional input (see Step 5)
                      │
                      ▼
           ┌──────────────────┐
           │  POST /submit/   │  ← Step 5: Submit mask/prompt for special operations
           │      modal       │
           └────────┬─────────┘
                    │ Returns: { "result": "task_id_3" }
                    ▼
           ┌──────────────────┐
           │ GET /task/{id}/  │  ← Step 6: Poll until SUCCESS
           │      fetch       │
           └──────────────────┘

Key concept: Buttons and customId

Every successful task returns a buttons array. Each button has a customId that you use to trigger the next action. Example response from /mj/task/\{id\}/fetch:

{
  "status": "SUCCESS",
  "imageUrl": "https://api.cometapi.com/mj/image/xxx",
  "buttons": [
    { "customId": "MJ::JOB::upsample::1::abc123", "label": "U1" },
    { "customId": "MJ::JOB::upsample::2::abc123", "label": "U2" },
    { "customId": "MJ::JOB::variation::1::abc123", "label": "V1" },
    { "customId": "MJ::JOB::reroll::0::abc123", "emoji": "🔄" }
  ]
}

customId is not a fixed value. It changes for every task. Always get it from the buttons array.

Button reference by stage

After IMAGINE (4-grid image)

These buttons are returned when your initial image generation completes:

Button	customId Pattern	Action	Result
U1-U4	`MJ::JOB::upsample::1::xxx`	Upscale single image	High-res single image
V1-V4	`MJ::JOB::variation::1::xxx`	Generate variations	New 4-grid
🔄	`MJ::JOB::reroll::0::xxx::SOLO`	Regenerate all	New 4-grid

After UPSCALE (single image)

After upscaling, you get access to editing tools:

Label	Needs Modal?
Upscale (Subtle) / Upscale (2x)	❌ No
Upscale (Creative) / Upscale (4x)	❌ No
Vary (Subtle) 🪄	❌ No
Vary (Strong) 🪄	❌ No
Vary (Region) 🖌️	✅ Yes (mask)
Zoom Out 2x / 1.5x 🔍	❌ No
Custom Zoom 🔍	✅ Yes (prompt)
⬅️➡️⬆️⬇️ Pan	❌ No
Animate 🎞️	❌ No
🔄 Reroll	❌ No

Note: Button labels and customId formats may vary depending on the MJ version specified in your prompt (e.g., --v 6.1 vs --v 5.2). Always read buttons from the API response.

Inpaint (Vary Region) button only appears after Upscale.

Complete example: Generate and upscale

Step 1: Submit imagine request

curl -X POST 'https://api.cometapi.com/mj/submit/imagine' \
  -H "Authorization: Bearer $COMETAPI_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "botType": "MID_JOURNEY",
    "prompt": "a cute cat --v 6.1",
    "accountFilter": { "modes": ["FAST"] }
  }'

Response:

{ "code": 1, "result": "1768464763141701" }

Step 2: Poll task status

curl -X GET 'https://api.cometapi.com/mj/task/1768464763141701/fetch' \
  -H "Authorization: Bearer $COMETAPI_KEY"

Response (when complete):

{
  "status": "SUCCESS",
  "imageUrl": "https://api.cometapi.com/mj/image/1768464763141701",
  "buttons": [
    { "customId": "MJ::JOB::upsample::1::5f20922e-xxx", "label": "U1" },
    { "customId": "MJ::JOB::upsample::2::5f20922e-xxx", "label": "U2" },
    ...
  ]
}

Step 3: Click U1 to upscale

curl -X POST 'https://api.cometapi.com/mj/submit/action' \
  -H "Authorization: Bearer $COMETAPI_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "taskId": "1768464763141701",
    "customId": "MJ::JOB::upsample::1::5f20922e-xxx"
  }'

Response:

{ "code": 1, "result": "1768464800000000" }

Step 4: Poll new task and get result

curl -X GET 'https://api.cometapi.com/mj/task/1768464800000000/fetch' \
  -H "Authorization: Bearer $COMETAPI_KEY"

When you call /mj/submit/action and the task status becomes MODAL instead of SUCCESS, you must call /mj/submit/modal to provide additional input.

Operation	Button	What to Submit
Inpaint	Vary (Region)	`maskBase64` (PNG mask) + `prompt`
Custom Zoom	🔍 Custom Zoom	`prompt` (e.g., “your prompt —zoom 2”)

Example: Inpaint Flow Start the Inpaint action:

curl -X POST 'https://api.cometapi.com/mj/submit/action' \
  -H "Authorization: Bearer $COMETAPI_KEY" \
  -H 'Content-Type: application/json' \
  -d '{"taskId": "<task_id>", "customId": "<custom_id>", "enableRemix": true}'

Query the new task once. A MODAL status means that the task needs the mask and prompt:

curl -X GET 'https://api.cometapi.com/mj/task/<task_id>/fetch' \
  -H "Authorization: Bearer $COMETAPI_KEY"

Submit the mask and prompt through the Modal API:

curl -X POST 'https://api.cometapi.com/mj/submit/modal' \
  -H "Authorization: Bearer $COMETAPI_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "taskId": "<task_id>",
    "prompt": "replace with golden crown",
    "maskBase64": "data:image/png;base64,<base64-encoded-png-mask>"
  }'

Speed mode selection

Add speed prefix to the path:

Mode	Path Prefix	Example
Fast	`/mj-fast`	`/mj-fast/mj/submit/imagine`
Turbo	`/mj-turbo`	`/mj-turbo/mj/submit/imagine`
Relax	(default)	`/mj/submit/imagine`

Other entry points

These APIs are independent entry points that don’t follow the imagine → action flow:

API	Purpose
`POST /mj/submit/blend`	Blend 2-5 images into one
`POST /mj/submit/describe`	Generate prompt from image
`POST /mj/submit/video`	Convert image to video
`POST /mj/submit/edits`	Edit image with mask

Troubleshooting tips

Based on the API design and workflow, here are common issues you may encounter:

Problem	Likely Cause	Solution
Can’t find Vary (Region) button	Looking at 4-grid image	Upscale first (click U1-U4), then check buttons
Task status stuck at `MODAL`	Operation requires additional input	Call `/mj/submit/modal` with required data
`customId` not working	Using outdated or hardcoded value	Always get fresh `customId` from `/mj/task/\{id\}/fetch` response
Empty `buttons` array	Task still in progress	Wait for `status: "SUCCESS"` before accessing buttons

Content moderation

API keys

Understand the core concept

The 4 core APIs

Complete workflow diagram

Key concept: Buttons and customId

Button reference by stage

After IMAGINE (4-grid image)

After UPSCALE (single image)

Complete example: Generate and upscale

Step 1: Submit imagine request

Step 2: Poll task status

Step 3: Click U1 to upscale

Step 4: Poll new task and get result

Speed mode selection

Other entry points

Troubleshooting tips

​Understand the core concept

​The 4 core APIs

​Complete workflow diagram

​Key concept: Buttons and customId

​Button reference by stage

​After IMAGINE (4-grid image)

​After UPSCALE (single image)

​Complete example: Generate and upscale

​Step 1: Submit imagine request

​Step 2: Poll task status

​Step 3: Click U1 to upscale

​Step 4: Poll new task and get result

​When is Modal required?

​Confirmed Modal operations

​Speed mode selection

​Other entry points

​Troubleshooting tips

Understand the core concept

The 4 core APIs

Complete workflow diagram

Key concept: Buttons and customId

Button reference by stage

After IMAGINE (4-grid image)

After UPSCALE (single image)

Complete example: Generate and upscale

Step 1: Submit imagine request

Step 2: Poll task status

Step 3: Click U1 to upscale

Step 4: Poll new task and get result

When is Modal required?

Confirmed Modal operations

Speed mode selection

Other entry points

Troubleshooting tips