Code intermediate · 3 min read

How to send image to OpenAI API in python

Q: How to send image to OpenAI API in python

Use the OpenAI Python SDK's client.chat.completions.create method with the image_url or image_base64 field in the message content to send images to the OpenAI API.

Direct answer

Use the OpenAI Python SDK's client.chat.completions.create method with the image_url or image_base64 field in the message content to send images to the OpenAI API.

Setup

Install

bash

pip install openai

Env vars

OPENAI_API_KEY

Imports

python

import os
from openai import OpenAI

Examples

inSend a PNG image URL to GPT-4o for caption generation.

outA descriptive caption of the image returned by the model.

inSend a base64-encoded JPEG image to GPT-4o for analysis.

outTextual analysis or description of the image content.

inSend an invalid image URL to GPT-4o.

outAPI error response indicating invalid image input.

Integration steps

Install the OpenAI Python SDK and set your API key in the environment variable OPENAI_API_KEY.
Import the OpenAI client and initialize it with the API key from os.environ.
Prepare the message content including the image data as a URL or base64 string in the message.
Call client.chat.completions.create with the appropriate model and messages array.
Extract the response text from response.choices[0].message.content.

Full code

python

import os
from openai import OpenAI

# Initialize client with API key from environment
client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])

# Example: Sending an image URL in the message content
image_url = "https://example.com/image.png"

messages = [
    {
        "role": "user",
        "content": f"Here is an image for analysis: {image_url}"
    }
]

response = client.chat.completions.create(
    model="gpt-4o",
    messages=messages
)

print("Response:", response.choices[0].message.content)

API trace

Request

json

{"model": "gpt-4o", "messages": [{"role": "user", "content": "Here is an image for analysis: https://example.com/image.png"}]}

Response

json

{"choices": [{"message": {"content": "This image shows a beautiful sunset over the mountains..."}}], "usage": {"total_tokens": 50}}

Extractresponse.choices[0].message.content

Variants

Send base64-encoded image data ›

Use this when you want to send image data directly without hosting it on a public URL.

python

import os
from openai import OpenAI
import base64

client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])

# Load image and encode to base64
with open("image.jpg", "rb") as img_file:
    b64_string = base64.b64encode(img_file.read()).decode("utf-8")

messages = [
    {
        "role": "user",
        "content": f"data:image/jpeg;base64,{b64_string}"
    }
]

response = client.chat.completions.create(
    model="gpt-4o",
    messages=messages
)

print("Response:", response.choices[0].message.content)

Streaming response for image analysis ›

Use streaming to get partial results immediately for large or complex image analysis tasks.

python

import os
from openai import OpenAI

client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])

image_url = "https://example.com/image.png"

messages = [{"role": "user", "content": f"Analyze this image: {image_url}"}]

response = client.chat.completions.create(
    model="gpt-4o",
    messages=messages,
    stream=True
)

for chunk in response:
    print(chunk.choices[0].message.content, end='')

Performance

Latency~1-3 seconds for typical image input processing with gpt-4o

Cost~$0.03 per 1,000 tokens for gpt-4o; image inputs may increase token usage

Rate limitsTier 1: 500 requests per minute / 30,000 tokens per minute

Compress or resize images before encoding to reduce token count.
Use concise prompts to minimize token usage.
Cache frequent image analyses to avoid repeated calls.

Approach	Latency	Cost/call	Best for
Image URL in message content	~1-3s	~$0.03 per 1k tokens	Quick image references with public URLs
Base64-encoded image data	~2-4s	~$0.04 per 1k tokens	Direct image data without hosting
Streaming response	Starts ~1s, continues	~$0.03 per 1k tokens	Long or complex image analysis with partial results

✓

Quick tip

Always encode images as base64 or provide a publicly accessible URL when sending images to the OpenAI API in Python.

⚠

Common mistake

Beginners often forget to encode binary images to base64 or provide accessible URLs, causing the API to reject the image input.

Verified 2026-04 · gpt-4o

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