Azure OpenAI returns 400 error for public image URLs

Question

Azure OpenAI returns 400 error for public image URLs

Leonardo Buffoni 0

Calls to the Azure OpenAI completion endpoint with image_url inputs return HTTP 400 error {'error': {'message': 'Failed to download image from [URL].', 'type': 'invalid_request_error', 'param': None, 'code': None}} for any publicly accessible URL (e.g. Wikipedia images reachable without authentication); the JSON payload and parameters are valid, and the issue occurs consistently across multiple requests and URLs, suggesting a failure in the service when fetching external images rather than a client-side error; please confirm if there are network restrictions, allowlist requirements, or known issues affecting external image retrieval.

Manas Mohanty 15,795 Microsoft External Staff Moderator

Hi Leonardo Buffoni

Could you share any sample usage code or screenshot on UI at your side.

Attaching trials on public image at my side.

Can you describe the image - https://learn.microsoft.com/en-us/azure/foundry/media/quickstarts/multimodal-vision/car-accident.png#lightbox

Official code for vision based model

import os
from openai import AzureOpenAI
api_base = os.getenv("AZURE_OPENAI_ENDPOINT")
api_key= os.getenv("AZURE_OPENAI_API_KEY")
deployment_name = '<your_deployment_name>'
api_version = '2023-12-01-preview' # this might change in the future
client = AzureOpenAI(
    api_key=api_key,  
    api_version=api_version,
    base_url=f"{api_base}/openai/deployments/{deployment_name}"
)
response = client.chat.completions.create(
    model=deployment_name,
    messages=[
        { "role": "system", "content": "You are a helpful assistant." },
        { "role": "user", "content": [  
            { 
                "type": "text", 
                "text": "Describe this picture:" 
            },
            { 
                "type": "image_url",
                "image_url": {
                    "url": "<image URL>"
                }
            }
        ] } 
    ],
    max_tokens=2000 
)
print(response)

Please share image urls and prompts used at your side in private message.

Thank you.

Manas Mohanty 15,795 Reputation points Microsoft External Staff Moderator

2026-03-26T16:44:21.01+00:00

Hi Leonardo Buffoni

Hope you found my inputs on using Base 64 converted images and other pointers helpful.

Please let us know if the issue was not resolved with proposed recommendations.

Thank you.

1 answer

Your answer

Manas Mohanty 15,795 Reputation points Microsoft External Staff Moderator

2026-03-25T17:56:35.1066667+00:00

Hi Leonardo Buffoni

Could you share any sample usage code or screenshot on UI at your side.

Attaching trials on public image at my side.

Can you describe the image - https://learn.microsoft.com/en-us/azure/foundry/media/quickstarts/multimodal-vision/car-accident.png#lightbox

Official code for vision based model

import os from openai import AzureOpenAI api_base = os.getenv("AZURE_OPENAI_ENDPOINT") api_key= os.getenv("AZURE_OPENAI_API_KEY") deployment_name = '<your_deployment_name>' api_version = '2023-12-01-preview' # this might change in the future client = AzureOpenAI( api_key=api_key, api_version=api_version, base_url=f"{api_base}/openai/deployments/{deployment_name}" ) response = client.chat.completions.create( model=deployment_name, messages=[ { "role": "system", "content": "You are a helpful assistant." }, { "role": "user", "content": [ { "type": "text", "text": "Describe this picture:" }, { "type": "image_url", "image_url": { "url": "<image URL>" } } ] } ], max_tokens=2000 ) print(response)

Please share image urls and prompts used at your side in private message.

Thank you.
Manas Mohanty 15,795 Reputation points Microsoft External Staff Moderator

2026-03-26T16:44:21.01+00:00

Hi Leonardo Buffoni

Hope you found my inputs on using Base 64 converted images and other pointers helpful.

Please let us know if the issue was not resolved with proposed recommendations.

Thank you.

Answer 1

Hi Leonardo Buffoni

Here are few reason behind above error

 HTTP 400 error {'error': {'message': 'Failed to download image from [URL].', 'type': 'invalid_request_error', 'param': None, 'code': None}}

Your OpenAI resource might be behind virtual network with no outbound access to public links allowed.

Blocked due to policy restriction.

Recommendation

you can convert the image url to base 64 formats.

   def encode_image_to_data_url(image_path: str) -> str:
       """
       Encode a local image to a data URL: data:image/<ext>;base64,<...>
       Azure OpenAI Responses API supports base64 images in vision prompts. [1](https://learn.microsoft.com/en-us/azure/foundry/openai/how-to/responses)[2](https://learn.microsoft.com/en-us/azure/ai-foundry/openai/how-to/responses?view=foundry-classic)
       """
       ext = os.path.splitext(image_path)[1].lower()
       if ext in [".jpg", ".jpeg"]:
           mime = "image/jpeg"
       elif ext == ".png":
           mime = "image/png"
       elif ext == ".webp":
           mime = "image/webp"
       else:
           raise ValueError("Use PNG, JPEG/JPG, or WEBP for vision image input.")
       with open(image_path, "rb") as f:
           b64 = base64.b64encode(f.read()).decode("utf-8")
       return f"data:{mime};base64,{b64}"
   if __name__ == "__main__":
       image_path = "path_to_your_image.jpg"
       data_url = encode_image_to_data_url(image_path)
       # For vision-enabled models, the doc shows:
       # - content: input_text + input_image (image_url string)
       # - Base64 encoded image approach also shown in the same doc. [1](https://learn.microsoft.com/en-us/azure/foundry/openai/how-to/responses)[2](https://learn.microsoft.com/en-us/azure/ai-foundry/openai/how-to/responses?view=foundry-classic)
       response = client.responses.create(
           model="gpt-4o",  # Use your deployed model name if required in your setup
           input=[
               {
                   "role": "user",
                   "content": [
                       {"type": "input_text", "text": "Describe what is in this image."},
                       {"type": "input_image", "image_url": data_url},
                   ],
               }
           ],
       )
       # Print the full response JSON
       print(response)

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Azure OpenAI returns 400 error for public image URLs

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