Why We Love Flask File Uploads (And You Should, Too!)

What Is Flask?

Flask is a Python-based lightweight or micro web framework for developing online applications. It comes with several essential tools and capabilities that make developing web applications a lot easier. One capability of Flask is that it supports the ability to do a Flask upload file from a client to a server and that is what we will cover in this article.

The framework is adaptable, and it doesn’t force you to use a specific structure or write a lot of boilerplate code. In short, it allows developers to be more creative. 

Why Does Everyone Love Flask?

Before we get into the basics—the nitty-gritty—of flask upload files, it’s important to note that there are other web application frameworks available as well, such as Django. 

In fact, the Django versus Flask debate is an age-old one that has gone on for years. Anyone comfortable with one should either stick with it to acquire expertise or try the other to broaden their tech stack. Flask is the most straightforward one to get started with, but you can use Django as well.

Though some argue that Flask is simpler and easier to learn than Django for developing web apps, there is another compelling argument to select Flask over Django.

Flask upload file enables your application to manage file uploading and serving flexibly and efficiently. You can establish several types of uploads — one for document assets, another for photographs, and so on — and the software can save them all in different locations and produce different URLs for them.

As developers in the cloud era, we’re moving away from traditional applications. Due to all of the built-in apps, running numerous Django servers with a microservices framework in place makes your operations heavy.

Online applications let users upload files. These files can be images, PDFs, audio CSV files, and so on. We’ll look at putting up a basic flask app that allows users to upload files in this tutorial.

However, with Filestack, you can find out how to upload different file types and formats hassle-free. 

What about Uploading a File in Flask?

Now, to understand Uploading a file in Flask, you must first understand the code’s flow. This means creating a template HTML file you can produce whenever you access a URL endpoint. This HTML includes elements like the submit button, enctype = “multipart/form-data,” the URL of the destination you will use when selecting the “Submit Radio” button, and the name of the file you are uploading using this form. 

Aside from the template file, we’ll need to write a Python script that consists of two functions that each serve a different purpose.

The first function is producing the home page’s URL endpoint, using the template file you created. You contain the file upload process within the second function, which includes the URL endpoint in the HTML template. When the file properly uploads, you return a success response code or any text that is appropriate for the use case.

Is It Easy to Upload a File with Python Flask?

Web developers typically need to upload files to a repository or a server. Cloud computing introduces the notion of treating networks as software rather than hardware, allowing web developers with minimum infrastructure/hardware knowledge to use these capabilities.

Amazon is the most prominent cloud computing provider, and Python is the preferred programming language for their cloud technology.

Uploading files is a regular job in web applications. We will show you how to achieve it with Python Flask in this guide. In fact, it’s quite easy to upload a file into a Flask file using the Flask file.

To publish the file to the URL, you’ll need an HTML form with the enctype property set to “multipart/form-data.”

The URL handler gets the file from the request. files [] object and stores it where it’s needed.

With Filestack’s powerful API tools, you can manage your upload and deliver content in the easiest way possible. 

How to Upload a File?


Each uploaded file saves to a different location on the server before saving to its permanent location.

You can hard code or retrieve the destination file name using the filename field of the file] request.files object. To acquire a safe version of it, however, use the secure filename() function.

In the Flask object’s customization options, you can specify the default upload directory location and the largest file size that can be uploaded.

Define the upload folder’s path.


Tells the maximum file size you can upload.


An “/upload” URL constraint displays “upload.html” in the templates directory, and a “/upload – file” URL rule invokes the “upload ()” function to execute the upload procedure in the following command.

There are two buttons in “upload.html”: a file selector and a push button.



      <form action = “http://localhost:5000/uploader” method = “POST” 

         enctype = “multipart/form-data”>

         <input type = “file” name = “file” />

         <input type = “submit”/>




Python Code

After choosing a file, click “Submit.” This calls the “upload file” URL with the form’s post function. You perform a save action with the underpinning function uploader().

Here is the Python script for the Flask program:

from flask import Flask, render_template, request

from werkzeug import secure_filename

app = Flask(__name__)


def upload_file():

   return render_template(‘upload.html’)

@app.route(‘/uploader’, methods = [‘GET’, ‘POST’])

def upload_file():

   if request.method == ‘POST’:

      f = request.files[‘file’]


      return ‘file uploaded successfully’

if __name__ == ‘__main__’:

   app.run(debug = True)


Ready to Get Started Uploading Files to a Flask Server?

You have learned about various file upload capabilities provided by Flask and the larger picture of how file uploads work. Now, you should be able to use the upload file feature and make sure there is a solid architecture in place.

Head over and get your FileStack Python SDK to get started.

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