Handling large file uploads is a common requirement in web applications. Flask provides a straightforward way to handle file uploads, but when dealing with large files, additional considerations are necessary. In this guide, we'll explore how to handle large file uploads in Flask efficiently, including optimizing file storage and streaming large files.

Step 1: Setting Up Your Flask Application

Start by setting up your Flask application and creating an HTML form for file uploads. Here's a sample directory structure:


Step 2: Creating the HTML Form

Create an HTML form that allows users to upload files. Here's a basic structure for your HTML template (upload.html):

<!DOCTYPE html>
<title>File Upload</title>
<h1>File Upload</h1>
<h2>Upload a Large File</h2>
<form action="/upload" method="post" enctype="multipart/form-data">
<input type="file" name="file" accept="*" required>
<button type="submit">Upload</button>

Step 3: Handling Large File Uploads

Create a route in your Flask application to handle large file uploads. Use streaming to process large files efficiently. Here's an example:

from flask import Flask, render_template, request
app = Flask(__name)
def index():
return render_template('upload.html')
@app.route('/upload', methods=['POST'])
def upload_file():
file = request.files['file']
if file:
# Process the uploaded file
with open('large_file.txt', 'wb') as f:
for chunk in
return 'File uploaded successfully'
return 'No file provided', 400
if __name__ == '__main__':

Step 4: Optimizing File Storage

When dealing with large files, consider optimizing file storage. You can store large files in an external storage system like Amazon S3 and use Flask-S3 for seamless integration.


Handling large file uploads in Flask requires careful consideration of file storage and efficient streaming. By following the steps in this guide, you can successfully implement large file uploads in your Flask applications. Remember to optimize your storage and processing for better performance and scalability.