List of supported file types for Azure OpenAI file upload

Question

Hi,

I am using the new Responses API and uploading files and adding to vector stores using the Assistants file upload (code snippet below).

However, I get errors for some file types that are supported by the OpenAI version of file storage, e.g. .pptx, .xlsx (see full list below from OpenAI docs).

Please can you share the full list of file types supported by Azure OpenAI file uploads as of today and if / when there are plans to expand to add more file types supported by OpenAI natively?

async def upload_file_to_azure(file_content: bytes, filename: str) -> str:
    """Upload file to Azure OpenAI and return file_id"""
    url = f"{AZURE_ENDPOINT}/openai/files"
    
    async with httpx.AsyncClient() as client:
        files = {"file": (filename, file_content, "application/octet-stream")}
        data = {"purpose": "assistants"}
        headers = {"api-key": API_KEY}
        params = {"api-version": "2025-04-01-preview"}
        
        response = await client.post(url, files=files, data=data, headers=headers, params=params)
        response.raise_for_status()
        return response.json()["id"]

OpenAI supported file types:

File format	MIME type
.c	text/x-c
.c	text/x-c
.cpp	text/x-c++
.cs	text/x-csharp
.css	text/css
.doc	application/msword
.docx	application/vnd.openxmlformats-officedocument.wordprocessingml.document
.go	text/x-golang
.html	text/html
.java	text/x-java
.js	text/javascript
.json	application/json
.md	text/markdown
.pdf	application/pdf
.php	text/x-php
.pptx	application/vnd.openxmlformats-officedocument.presentationml.presentation
.py	text/x-python
.py	text/x-script.python
.rb	text/x-ruby
.sh	application/x-sh
.tex	text/x-tex
.ts	application/typescript
.txt	text/plain

Answer 1

Hello,

Welcome to Microsoft Q&A,

You're observing a key difference between OpenAI’s file support and what’s currently available in Azure OpenAI’s Assistants API (2025-04-01-preview).

1. The OpenAI platform supports a wide range of file types, including .pptx, .xlsx, .csv, .json, .sh, etc.
2. Azure OpenAI's support for file uploads in the Assistants API is more limited and evolving.
3. As of today, Azure OpenAI does not support .xlsx uploads for the assistant's purpose, even though .pptx and .pdf are supported in certain tools like File Search.

.xlsx, .csv, and .xls are not currently supported by Azure OpenAI file uploads, even though OpenAI’s API accepts them.

You can check all supported file type here for assistant here.

https://learn.microsoft.com/en-us/azure/ai-services/openai/how-to/file-search?web=1&tabs=python#supported-file-types

https://learn.microsoft.com/en-us/azure/ai-services/openai/how-to/assistant

1. Azure has not published a public roadmap for expanding file type support to include .xlsx, .csv, or .xls.
2. However, as new preview APIs are released (e.g., 2025-06-01-preview or later), additional file types may be added, especially as parity with OpenAI’s platform improves.

https://learn.microsoft.com/en-us/azure/ai-services/openai/whats-new

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