FastAPI File Validators

A simple, lightweight, and flexible decorator-based file validation library for FastAPI. Easily validate uploaded file extensions and file sizes before hitting your endpoint logic.

🚀 Installation

Install via pip:

pip install fastapi-file-validators

Or install locally for development:

pip install -e .

📦 Usage

1. Validate File Extension

Ensure that the uploaded file matches specific allowed extensions. If the extension is invalid or missing, it automatically raises an HTTP 415 Unsupported Media Type or HTTP 400 Bad Request.

from fastapi import FastAPI, UploadFile, File
from file_validator import file_extension_validator

app = FastAPI()

@app.post("/upload/image")
@file_extension_validator(file_arg_name="file", file_extensions={"jpg", "jpeg", "png"})
async def upload_image(file: UploadFile = File(...)):
    return {"filename": file.filename, "message": "Extension validated successfully!"}

2. Validate File Size

Restrict the maximum size of an uploaded file in Megabytes (MB). If the file exceeds the limit, it automatically raises an HTTP 413 Content Too Large.

from fastapi import FastAPI, UploadFile, File
from file_validator import file_size_validator

app = FastAPI()

@app.post("/upload/large-file")
@file_size_validator(file_arg_name="file", max_size_mb=10)  # Limit to 10MB
async def upload_large_file(file: UploadFile = File(...)):
    return {"size": file.size, "message": "Size validated successfully!"}

⚙️ Configuration

Exception Handling

The decorators raise standard FastAPI HTTPExceptions. You can expect the following responses when validation fails:

📄 License

MIT License