> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apiyi.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Text-to-Image API Reference
> Seedream text-to-image API reference and live Playground — pure text prompts, 1K/2K/3K/4K and exact pixel sizes, three versions on a single endpoint
The interactive Playground on the right lets you call the API directly. Set **Authorization** to your API key (format: `Bearer sk-xxx`), enter a prompt, pick a model and size, and hit send.
**Scope**: this page covers pure text-to-image (no `image` field). For reference-image editing, multi-image fusion, or batch sequence generation, see [Image Editing](/en/api-capabilities/seedream-image/image-edit) — same endpoint, just different parameters.
**🖥️ Browser Playground limitation (b64\_json mode only)**
In the default `response_format: "url"` mode, the Playground works fine (the response is just a temporary BytePlus TOS link). If you switch to `response_format: "b64_json"`, the response contains a multi-MB base64 string and the browser Playground may show `请求时发生错误: unable to complete request` — **the request actually succeeded**; the browser just can't render such a long base64 string.
**Recommended workflow**:
* Just want to view the image? **Keep the default `url` mode** — the Playground returns the link directly (remember to download to your own storage within 24 hours).
* Need b64\_json? **Copy the code sample below and run it locally** — the code will decode and save the image to a file automatically.
**⚠️ Resolution tiers vary by version**
* `seedream-5-0-pro-260628` — presets `1K` / `2K` plus exact WxH up to 4.19M total pixels (at 16:9 the longest edge reaches 2720×1530, verified; no 3K/4K presets; `sequential_image_generation` / `stream` not accepted — passing them returns 400; \~2 min per image)
* `seedream-5-0-260128` — `2K` / `3K` only (no 4K)
* `seedream-4-5-251128` — `2K` / `4K`
* `seedream-4-0-250828` — `1K` / `2K` / `4K`
**Unsupported sizes return 400**. Exact pixels must satisfy total ∈ \[1280×720, 4096×4096] and aspect ratio ∈ \[1/16, 16].
All image APIs are **synchronous** — there is no task ID to poll, and if your client disconnects the result is lost while the request is still billed. Set a generous timeout for this model; see [Image API Essentials & Best Practices](/en/api-capabilities/image-api-best-practices).
## Code Examples
### Python (OpenAI SDK)
```python theme={null}
from openai import OpenAI
client = OpenAI(
api_key="sk-your-api-key",
base_url="https://api.apiyi.com/v1"
)
resp = client.images.generate(
model="seedream-5-0-260128",
prompt="A modern tech product launch poster with bold typography, sleek smartphone on gradient background, text: 'Innovation 2026', ultra detailed, professional",
size="2K",
response_format="url",
extra_body={
"output_format": "png",
"watermark": False,
}
)
print(resp.data[0].url)
```
### Python (raw requests)
```python theme={null}
import requests
API_KEY = "sk-your-api-key"
response = requests.post(
"https://api.apiyi.com/v1/images/generations",
headers={
"Authorization": f"Bearer {API_KEY}",
"Content-Type": "application/json"
},
json={
"model": "seedream-5-0-260128",
"prompt": "A serene Japanese garden with cherry blossoms, koi pond, traditional wooden bridge, golden hour, ultra detailed",
"size": "2K",
"response_format": "url",
"watermark": False
},
timeout=60 # ~15s typical, 4K + hd may reach 30-60s
).json()
print(response["data"][0]["url"])
```
### cURL
```bash theme={null}
curl -X POST "https://api.apiyi.com/v1/images/generations" \
-H "Authorization: Bearer sk-your-api-key" \
-H "Content-Type: application/json" \
-d '{
"model": "seedream-5-0-260128",
"prompt": "A futuristic cityscape at night with neon lights and flying vehicles, cyberpunk style, high detail",
"size": "2K",
"response_format": "url",
"watermark": false
}'
```
### Node.js (fetch)
```javascript theme={null}
const resp = await fetch('https://api.apiyi.com/v1/images/generations', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
'Authorization': 'Bearer sk-your-api-key'
},
body: JSON.stringify({
model: 'seedream-5-0-260128',
prompt: 'Minimalist line-art logo of a cat, monochrome, vector style',
size: '2K',
response_format: 'url',
output_format: 'png',
watermark: false
})
});
const { data } = await resp.json();
console.log(data[0].url);
```
### Browser JavaScript
```javascript theme={null}
{/* Demo only — proxy through your backend in production to avoid leaking the key */}
const resp = await fetch('https://api.apiyi.com/v1/images/generations', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
'Authorization': 'Bearer sk-your-api-key'
},
body: JSON.stringify({
model: 'seedream-5-0-260128',
prompt: 'Watercolor northern lights over snowy mountains',
size: '2K'
})
});
const { data } = await resp.json();
document.getElementById('img').src = data[0].url;
```
## Parameter Reference
| Parameter | Type | Required | Default | Description |
| ----------------- | ------- | -------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `model` | string | yes | — | `seedream-5-0-260128` / `seedream-4-5-251128` / `seedream-4-0-250828` / `seedream-5-0-pro-260628` (pro tier, \$0.12/request) |
| `prompt` | string | yes | — | Prompt text. Supports English and Chinese. Be detailed about scene, style, lighting. |
| `size` | string | no | `2K` | Preset tier (varies by version) or exact pixels `WxH` |
| `response_format` | string | no | `url` | `url` returns a signed link; `b64_json` returns a plain base64 string |
| `output_format` | string | no | `jpeg` | 5.0 supports `png` / `jpeg`; 4.5 / 4.0 only `jpeg` (pass via `extra_body` in OpenAI SDK) |
| `n` | integer | — | — | ⚠️ **Not supported upstream**: the parameter is silently ignored — you still get 1 image and are billed for 1. For multi-image output use `sequential_image_generation` (billed per generated image), see [Image Editing](/en/api-capabilities/seedream-image/image-edit) |
| `seed` | integer | — | — | ⚠️ Officially supported only by seedream-3-0-t2i; ignored by the current 4.x / 5.x models |
| `watermark` | boolean | no | varies | Whether to include the BytePlus watermark (set `false` for commercial use) |
| `stream` | boolean | no | `false` | Streaming output, useful for long prompts + high resolution |
Detailed parameter constraints, allowed values, and examples are visible in the Playground panel on the right. **Editing / multi-image parameters (`image`, `sequential_image_generation`, etc.) are documented on the [Image Editing](/en/api-capabilities/seedream-image/image-edit) page.**
## Response Format
```json theme={null}
{
"model": "seedream-5-0-260128",
"created": 1768518000,
"data": [
{
"url": "https://ark-content-generation-v2-ap-southeast-1.tos-ap-southeast-1.bytepluses.com/seedream-5-0/.../image.png",
"size": "2048x2048"
}
],
"usage": {
"generated_images": 1,
"output_tokens": 6240,
"total_tokens": 6240
}
}
```
**⚠️ Response field caveats**
* When `response_format=url`, `data[].url` is a **temporary signed BytePlus TOS URL** (typically valid for 24 hours). For production, download immediately to your own storage.
* When `response_format=b64_json`, `data[].b64_json` is a **plain base64 string**, **without** the `data:image/...;base64,` prefix. Decode it (`base64.b64decode`) for file output, or prepend the prefix yourself for browser rendering.
* `data[].size` reflects the **actual output size**, which may differ slightly from the requested `size` after the model's aspect-ratio normalization.
`usage.generated_images` reflects the billed image count. Seedream bills per image; `output_tokens` / `total_tokens` are observability metrics and do not affect billing.
## OpenAPI
````yaml api-reference/seedream-image-generate-openapi-en.yaml POST /v1/images/generations
openapi: 3.1.0
info:
title: Seedream Text-to-Image API
description: >
BytePlus ModelArk Seedream image generation models — text-to-image endpoint
(no `image` field).
- Active versions unified: `seedream-5-0-260128` / `seedream-4-5-251128` /
`seedream-4-0-250828` / `seedream-5-0-pro-260628` (pro tier, \$0.12 per
request, ~2 min per image)
- Resolution tiers vary by version (5.0: 2K/3K; 4.5: 2K/4K; 4.0: 1K/2K/4K;
5.0-pro: 1K/2K plus WxH up to 4.19M total px, longest edge ~2720 at 16:9)
- Output format: 5.0 / 5.0-pro support png/jpeg; 4.5/4.0 only jpeg
- 5.0-pro does not accept `sequential_image_generation` / `stream` — passing
them returns 400
- Latency ≈ 15s per image, may extend to 30-60s for 4K + hd
- Default 500 RPM (Max Images per Minute)
- For editing, multi-image fusion, or batch sequence generation, see [Image
Editing](/en/api-capabilities/seedream-image/image-edit) (same endpoint,
different params)
**Auth**: add `Authorization: Bearer YOUR_API_KEY` to the request header.
**Get API Key**: visit [APIYI Console](https://api.apiyi.com/token) to
create a token.
version: 1.0.0
servers:
- url: https://api.apiyi.com
description: Primary endpoint
- url: https://vip.apiyi.com
description: Backup endpoint
security:
- bearerAuth: []
paths:
/v1/images/generations:
post:
tags:
- Text-to-Image
summary: 'Text-to-Image: generate an image from a text prompt'
description: >
Generate an image with the Seedream models from a text prompt.
- Required: `model`, `prompt`
- Optional: `size`, `response_format`, `output_format`, `watermark`,
`stream`
- Note: OpenAI's `n` parameter is not supported upstream (silently
ignored — you still get 1 image); for multi-image output use
`sequential_image_generation`
- Resolution tiers vary by version — see [Overview / Technical
Specs](/en/api-capabilities/seedream-image/overview#technical-specs)
- For reference-image editing or multi-image fusion, use the same
endpoint with `image` and `sequential_image_generation` — see [Image
Editing](/en/api-capabilities/seedream-image/image-edit)
operationId: generateSeedreamTextToImage
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/SeedreamGenerateRequest'
example:
model: seedream-5-0-260128
prompt: >-
A modern tech product launch poster, sleek smartphone on
gradient background, text: 'Innovation 2026', ultra detailed,
professional
size: 2K
response_format: url
output_format: png
watermark: false
responses:
'200':
description: Image generated successfully
content:
application/json:
schema:
$ref: '#/components/schemas/SeedreamImageResponse'
'400':
description: >-
Invalid parameters (size not supported by this version, pixel out of
range, aspect ratio out of bounds)
'401':
description: Unauthorized — invalid API key
'403':
description: Blocked by content moderation
'429':
description: Rate limit (default 500 RPM) or insufficient balance
'500':
description: Internal server error
security:
- bearerAuth: []
components:
schemas:
SeedreamGenerateRequest:
type: object
required:
- model
- prompt
properties:
model:
type: string
description: Model ID
enum:
- seedream-5-0-260128
- seedream-5-0-lite-260128
- seedream-4-5-251128
- seedream-4-0-250828
- seedream-5-0-pro-260628
default: seedream-5-0-260128
prompt:
type: string
description: >-
Prompt, supports both English and Chinese. Describe scene, style,
and lighting in detail for better results.
example: >-
A serene Japanese garden with cherry blossoms, koi pond, traditional
bridge, golden hour, ultra detailed
size:
type: string
description: >
Output size. Preset tiers (vary by version):
- `1K` (~1024×1024) — 4.0 only
- `2K` (~2048×2048) — 5.0 / 4.5 / 4.0
- `3K` (~3072×3072) — 5.0 only
- `4K` (~4096×4096) — 4.5 / 4.0
Or exact pixel size `WxH`, total pixels ∈ \[1280×720, 4096×4096\],
aspect ratio ∈ \[1/16, 16\]
example: 2K
default: 2K
response_format:
type: string
description: >-
url returns a temp signed link (24h validity); b64_json returns
plain base64 (no data: prefix)
enum:
- url
- b64_json
default: url
output_format:
type: string
description: Output format. 5.0 supports png/jpeg; 4.5/4.0 only jpeg
enum:
- png
- jpeg
default: jpeg
seed:
type: integer
description: >-
Random seed. Note: officially supported only by seedream-3-0-t2i;
ignored by the current 4.x / 5.x models
example: 42
watermark:
type: boolean
description: >-
Whether to include the BytePlus watermark. Set to false for
commercial use
default: false
stream:
type: boolean
description: >-
Enable streaming output. Useful for long prompts and high-resolution
generation
default: false
SeedreamImageResponse:
type: object
properties:
model:
type: string
example: seedream-5-0-260128
created:
type: integer
description: Unix timestamp
example: 1768518000
data:
type: array
items:
type: object
properties:
url:
type: string
description: >-
Image URL (returned when response_format=url; signed temp URL
valid for 24h)
example: >-
https://ark-content-generation-v2-ap-southeast-1.tos-ap-southeast-1.bytepluses.com/seedream-5-0/.../image.png
b64_json:
type: string
description: >-
Plain base64 string (no data:image/...;base64, prefix).
Returned when response_format=b64_json.
size:
type: string
description: >-
Actual output size, may differ slightly from requested due to
aspect-ratio adjustments
example: 2048x2048
usage:
type: object
properties:
generated_images:
type: integer
description: Actual billed image count
example: 1
output_tokens:
type: integer
example: 6240
total_tokens:
type: integer
example: 6240
securitySchemes:
bearerAuth:
type: http
scheme: bearer
description: API Key obtained from APIYI Console
````