Seedream 4.0 API

ByteDance Seedream 4.0 image generation API for text-to-image and image-to-image workflows with 1K, 2K, and 4K output presets

Overview

Seedream 4.0 is a ByteDance image model for text-to-image generation and reference-guided image generation. It supports 1K, 2K, and 4K output presets, up to 15 generated images per task, optional sequential generation, and prompt optimization with standard or fast.

Capability	Value
Model ID	seedream-4-0
Modes	text-to-image, image-to-image
Prompt length	1-5000 characters
Reference images	1-14 URLs for image-to-image
Images per task	max_images is required, 1-15; for image-to-image, image_urls count + max_images must be less than or equal to 15
Resolution tiers	1K, 2K, 4K
Aspect ratios	1:1, 2:3, 3:2, 4:3, 3:4, 9:16, 16:9, 21:9
Size input	1K, 2K, 4K, 2048x2048, 2048X2048, 2048*2048
Sequential generation	disabled, auto
Prompt optimization	standard, fast

Endpoint and authentication

Base URL:

https://api.apixo.ai/api/v1

Method	Endpoint	Purpose
POST	/generateTask/seedream-4-0	Submit a generation task
GET	/statusTask/seedream-4-0?taskId={taskId}	Poll task status and retrieve results

All requests require your APIXO API key:

Authorization: Bearer YOUR_API_KEY

Submit requests also require:

Content-Type: application/json

Copy-paste async quickstart

This minimal request submits a text-to-image task and returns a taskId.

curl -X POST "https://api.apixo.ai/api/v1/generateTask/seedream-4-0" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "input": {
      "mode": "text-to-image",
      "prompt": "a sunrise train passing through snowy hills",
      "max_images": 2,
      "resolution": "1K",
      "aspect_ratio": "16:9",
      "prompt_optimize_mode": "fast"
    }
  }'

Successful response:

{
  "code": 200,
  "message": "success",
  "data": {
    "taskId": "task_12345678"
  }
}

Save the taskId; you need it to poll for the final result.

Request body

Text-to-image

{
  "input": {
    "mode": "text-to-image",
    "prompt": "a clean architectural concept of a coastal library",
    "max_images": 2,
    "resolution": "1K",
    "aspect_ratio": "16:9",
    "prompt_optimize_mode": "fast"
  }
}

Image-to-image

{
  "input": {
    "mode": "image-to-image",
    "prompt": "turn this sketch into a cinematic concept frame",
    "image_urls": [
      "https://example.com/reference-1.png"
    ],
    "max_images": 2,
    "resolution": "2K",
    "aspect_ratio": "3:4",
    "sequential_image_generation": "auto",
    "prompt_optimize_mode": "standard"
  }
}

Explicit size

{
  "input": {
    "mode": "text-to-image",
    "prompt": "an editorial interior still",
    "max_images": 1,
    "size": "2048*2048"
  }
}

Parameters

request_type · string · default: "async"

Result delivery mode. Use async for polling with statusTask, or callback for webhook delivery.

callback_url · string

Required when request_type is callback. Must be a public HTTPS URL that can receive the final task payload. See Webhooks.

input · object · required

Seedream 4.0 input parameters.

Show properties

mode · string · required

Generation mode. Supported values: text-to-image, image-to-image.

prompt · string · required

Text prompt describing the desired image or edit. Supports 1-5000 characters after trimming whitespace.

max_images · integer · required

Number of images to request. Supported range: 1-15. For image-to-image, the number of reference images in image_urls plus max_images must not exceed 15.

image_urls · string[]

Reference image URLs. Required for image-to-image. Supports 1-14 URLs. URLs should be public, directly accessible image files. For image-to-image, image_urls count + max_images must be less than or equal to 15.

resolution · string · default: "2K"

Output resolution preset. Supported values: 1K, 2K, 4K. When resolution + aspect_ratio and size are both provided, resolution + aspect_ratio takes precedence.

aspect_ratio · string

Optional output aspect ratio. Supported values: 1:1, 2:3, 3:2, 4:3, 3:4, 9:16, 16:9, 21:9.

size · string

Optional explicit size or preset token. Preset tokens are case-insensitive and support 1K, 2K, and 4K. Pixel strings accept x, X, or * separators, such as 2048x2048, 2048X2048, or 2048*2048. Custom pixel sizes must use 16-pixel granularity, keep aspect ratio between 1/16 and 16, and keep total pixels between 921,600 and 16,777,216 (1280x720 to 4096x4096 equivalent). Unsupported custom values may be adjusted to the nearest supported output size.

sequential_image_generation · string · default: "disabled"

Sequential image mode. Supported values: disabled, auto.

prompt_optimize_mode · string · default: "standard"

Prompt optimization mode. Supported values: standard, fast.

nsfw_checker · boolean · default: "false"

Enables content safety filtering for this request. Defaults to false. Must be a boolean when provided.

Size presets from resolution + aspect_ratio

When aspect_ratio is provided, APIXO maps resolution and aspect_ratio to these output dimensions:

Aspect ratio	1K size	2K size	4K size
1:1	1024x1024	2048x2048	4096x4096
2:3	832x1248	1664x2496	3328x4992
3:2	1248x832	2496x1664	4992x3328
3:4	864x1152	1728x2304	3520x4704
4:3	1152x864	2304x1728	4704x3520
9:16	736x1312	1600x2848	3040x5504
16:9	1312x736	2848x1600	5504x3040
21:9	1568x672	3136x1344	6240x2656

Polling and delivery guidance

Seedream 4.0 tasks are asynchronous.

Resolution	Typical generation time	Recommended first poll	Poll interval
1K	20s-30s	15s after task creation	3s
2K	25s-35s	20s after task creation	3s-5s
4K	40s-55s	30s after task creation	5s

For production systems, prefer callback_url instead of tight polling loops.

Billing

Seedream 4.0 is billed per generated image. The current public APIXO price is a single flat rate for this model.

Unit	APIXO price
Per generated image	$0.0290 / image

Billing behavior:

precharge = requested max_images * unit price
final charge = successful images * unit price

If fewer images succeed than requested, APIXO automatically adjusts the final charge to the actual number of successful outputs.

Related links

• Image Models
• Generation API Overview
• Generate Task
• Status Task
• Webhooks
• Error Codes
• Pricing