DALL-E 3 API Calls Returning 403 Errors Intermittently

Question

DALL-E 3 API Calls Returning 403 Errors Intermittently

Kalle Gerarts 20

Hello,

The REST API calls for DALL-E 3 deployments intermittently return a 403 error. Initially, calling the deployment's endpoint successfully returns the URL for the generated image. However, when attempting to download the image using the returned URL, there are two or three successful attempts followed by a 403 error, which indicates an authorization issue. After a brief period, one or two attempts succeed again, and this pattern continues. What could be causing this intermittent authorization problem? My first idea was a rate limit, but in this case the REST API call should return a 429 Error, if the documentation is correct. My second idea was that it is a timing problem, but the running URLs are still running after a day.

The code is written in C# and I do NOT use the Azure Open API but calling the endpoint on my own:

"https://{0}.openai.azure.com/openai/deployments/{1}/images/generations?api-version={2}"

I copied the returned URL to the browser and it returned as well with an error. It contains bit more information than only "AuthenticationFailed":

https://dalleprodsec.blob.core.windows.net/private/images/67934f20-1848-4470-974b-6eebd1eaf1c5/generated_00.png?se=2025-04-02T06:10:27Z&sig=fDuyzsL+d3Ci3lK/PxOryOLTaj1FG0jAAi8u6fAv27g=&ske=2025-04-02T19:48:02Z&skoid=e52d5ed7-0657-4f62-bc12-7e5dbb260a96&sks=b&skt=2025-03-26T19:48:02Z&sktid=33e01921-4d64-4f8c-a055-5bdaffd5e33d&skv=2020-10-02&sp=r&spr=https&sr=b&sv=2020-10-02

This XML file does not appear to have any style information associated with it. The document tree is shown below.

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Thank you for taking time to help.

Kalle Gerarts 20 Reputation points

2025-04-01T08:15:48.9766667+00:00

Addition:

I just changed the response_format to b64_json, which returns the generated image directly on REST API Call. This seems to work: I created 5 or 6 images without any error.

Nevertheless I'm interested in solving the problem with the URLs. This could be an appropriate solution if the images get bigger.
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Kalle Gerarts 20 Reputation points

2025-04-02T09:08:38.2366667+00:00
Thank you for your answer. Sharing sample code is not so easy. We authenticate with a PublicClientApplication using Microsoft Graph. We did that already before AI came up. So we do NOT use the Azure AI OpenAI API. We are call the REST-API endpoint directly as shown in my original question.

"https://{0}.openai.azure.com/openai/deployments/{1}/images/generations?api-version={2}"

I wanted to run your code to check if there is a general problem accessing the generated image. I would have had to change it a bit because your code downloads the same image for six times. If can download an image once, I can download it for several times even after days. The problem occurs when generating a new image each time.

But ...

Inspired of your solution, first, I changed my code and used the webclient to download the picture instead of using the picturebox's Load method.

//old //this.GeneratedImagePicBox.Load(imageUris.First()); //new using (WebClient webClient = new WebClient()) { byte[] imageBytes = webClient.DownloadData(imageUris.First()); using (var ms = new System.IO.MemoryStream(imageBytes)) { Image image = Image.FromStream(ms); this.GeneratedImagePicBox.Image = image; } }

And this is working. The problem/issue seems to sit in the Load method. If I have more time I think I'm going to have a look with Fiddler what the pictorebox.Load method is sending. I already had a look to the code, the picturebox does nearly the same but uses webclient.OpenRead instead of DownloadData. Maybe this makes a difference.

Anyway, my problem seems to be solved.

Thanks a lot.
Manas Mohanty 5,620 Reputation points Microsoft External Staff Moderator

2025-04-02T09:11:28.75+00:00

Hi Kalle Gerarts

Thank you for confirming. Could you accept the below answer if it helped.

Thank you.

Accepted answer

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Your answer

Kalle Gerarts 20 Reputation points

2025-04-01T08:15:48.9766667+00:00

Addition:

I just changed the response_format to b64_json, which returns the generated image directly on REST API Call. This seems to work: I created 5 or 6 images without any error.

Nevertheless I'm interested in solving the problem with the URLs. This could be an appropriate solution if the images get bigger.
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Kalle Gerarts 20 Reputation points

2025-04-02T09:08:38.2366667+00:00

Thank you for your answer. Sharing sample code is not so easy. We authenticate with a PublicClientApplication using Microsoft Graph. We did that already before AI came up. So we do NOT use the Azure AI OpenAI API. We are call the REST-API endpoint directly as shown in my original question.

"https://{0}.openai.azure.com/openai/deployments/{1}/images/generations?api-version={2}"

I wanted to run your code to check if there is a general problem accessing the generated image. I would have had to change it a bit because your code downloads the same image for six times. If can download an image once, I can download it for several times even after days. The problem occurs when generating a new image each time.

But ...

Inspired of your solution, first, I changed my code and used the webclient to download the picture instead of using the picturebox's Load method.

//old //this.GeneratedImagePicBox.Load(imageUris.First()); //new using (WebClient webClient = new WebClient()) { byte[] imageBytes = webClient.DownloadData(imageUris.First()); using (var ms = new System.IO.MemoryStream(imageBytes)) { Image image = Image.FromStream(ms); this.GeneratedImagePicBox.Image = image; } }

And this is working. The problem/issue seems to sit in the Load method. If I have more time I think I'm going to have a look with Fiddler what the pictorebox.Load method is sending. I already had a look to the code, the picturebox does nearly the same but uses webclient.OpenRead instead of DownloadData. Maybe this makes a difference.

Anyway, my problem seems to be solved.

Thanks a lot.
Manas Mohanty 5,620 Reputation points Microsoft External Staff Moderator

2025-04-02T09:11:28.75+00:00

Hi Kalle Gerarts

Thank you for confirming. Could you accept the below answer if it helped.

Thank you.

Answer 1

Hi Kalle Gerarts

Could you share sample code for replicating the issue.

I was able to download 5 images iteratively from same image source using below source code with .NET SDK 8 (without 403 or 429 issue)

//dalle image generation
using System;
using System.IO;
using System.Net.Http;
using System.Threading.Tasks;
using Azure;
using Azure.AI.OpenAI;
using Azure.Identity;

using OpenAI.Images;
using static System.Environment;

class Program
{
    static async Task Main(string[] args)
    {
        string endpoint = "https://<sourcename>.openai.azure.com/";
        string key = "<apikey>";

    
        // Use the recommended keyless credential instead of the AzureKeyCredential credential.
        //AzureOpenAIClient openAIClient = new AzureOpenAIClient(new Uri(endpoint), new DefaultAzureCredential());
        AzureOpenAIClient openAIClient = new AzureOpenAIClient(new Uri(endpoint), new AzureKeyCredential(key));

        // This must match the custom deployment name you chose for your model
        ImageClient chatClient = openAIClient.GetImageClient("dall-e-3");

        var imageGeneration = await chatClient.GenerateImageAsync(
            "a happy monkey sitting in a tree, in watercolor",
            new ImageGenerationOptions()
            {
                Size = GeneratedImageSize.W1024xH1024
            }
        );

       
        string imageUri = imageGeneration.Value.ImageUri.ToString();
        Console.WriteLine(imageUri);

        // Download and save the image to the local machine
        using (HttpClient client = new HttpClient())
        {
            HttpResponseMessage response = await client.GetAsync(imageUri);
            if (response.IsSuccessStatusCode)
            {
                byte[] imageBytes = await response.Content.ReadAsByteArrayAsync();
                await File.WriteAllBytesAsync("downloaded_image.jpg", imageBytes);
                await File.WriteAllBytesAsync("downloaded_image1.jpg", imageBytes);
                await File.WriteAllBytesAsync("downloaded_image2.jpg", imageBytes);
                await File.WriteAllBytesAsync("downloaded_image3.jpg", imageBytes);
                await File.WriteAllBytesAsync("downloaded_image4.jpg", imageBytes);
                await File.WriteAllBytesAsync("downloaded_image5.jpg", imageBytes);
                Console.WriteLine("Image successfully downloaded and saved as 'downloaded_image.jpg'.");
            }
            else
            {
                Console.WriteLine("Failed to download the image.");
            }
        }
    }
}

Key Changes -

        string imageUri = imageGeneration.Value.ImageUri.ToString();

Are you using a virtual network protected resource by any chance (there might be intermitted network block on proxy or firewall)

Thank you

Kalle Gerarts 20 Reputation points

2025-04-02T09:14:19.35+00:00

Using the webclient to download the picture instead of using the picturebox's Load method solved the problem.

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DALL-E 3 API Calls Returning 403 Errors Intermittently

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