Flask Download Button

Flask-Download-Btn defines a SQLALchemy Mixin for creating Bootstrap download buttons in a Flask application.

Its features include:

  1. Automatic enabling and disabling. A download button is automatically disabled on click and re-enabled on download completion.
  2. CSRF protection. The download button checks for a CSRF authentication token to ensure the client has permission to download the requested file.
  3. Web form handling. Download buttons are responsive to web forms.
  4. Pre-download operations. Download buttons can easily perform operations before files are downloaded, making it easy to create temporary download files.
  5. Progress bar. Update your clients on download progress with server sent events.


$ pip install flask-download-btn


Our folder structure will look like:


In templates/index.html, paste the following Jinja template:

        <!-- include Bootstrap CSS and Javascript -->
        <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css">
        <!-- render the download button and progress bar -->
        {{ download_btn.render_btn() | safe }}
        {{ download_btn.render_progress() | safe }}
        <script src="https://code.jquery.com/jquery-3.4.1.min.js"></script>
        <script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js"></script>
        <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js"></script>
        <!-- include download button script -->
        {{ download_btn.render_script() | safe }}

In app.py:

from flask_download_btn import DownloadBtnManager, DownloadBtnMixin

from flask import Flask, render_template, session
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.ext.orderinglist import ordering_list

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///:memory:'
db = SQLAlchemy(app)
# initialize download button manager with application and database
download_btn_manager = DownloadBtnManager(app, db=db)

# create download button model and register it with the manager
class DownloadBtn(DownloadBtnMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)

# create the database and clear the session when the app starts
def before_first_request():

HELLO_WORLD_URL = 'https://test-bucket2357.s3.us-east-2.amazonaws.com/hello_world.txt'

# basic use
def index():
    btn = DownloadBtn()
    btn.downloads = [(HELLO_WORLD_URL, 'hello_world.txt')]
    return render_template('index.html', download_btn=btn)

Run the app with:

$ python app.py

And navigate to http://localhost:5000/. Click the download button to download a text file with 'Hello, World!'.


  author = {Dillon Bowen},
  title = {Flask-Download-Btn},
  url = {https://dsbowen.github.io/flask-download-btn/},
  date = {2020-06-17},


Users must cite this package in any publications which use it.

It is licensed with the MIT License.