Deploying Flask App - With Heroku

Step by Step instructions to deploy Flask app with Heroku


4 min read

Heroku is the simple and easiest way to deploy your backend APIs. The blog consists of step-by-step instructions to deploy your application along with a project template that makes it easy for you to organize your applications.

Note:: The following deployment process is followed by my PythonToProject Bootcamp students to deploy the API that they build over a 4 week period right from idea scoping to Design to development

Table of Contents

1. Create Heroku Account

  • Go to
  • Signup and create an account
  • Login to the account

If you are creating the account for the first time, choose Hobby Free Plan

2. Create New app

  • Once you are in the dashboard, click on the New button & then Create New App.
  • Give an app name, choose a region, ignore the pipeline
  • Click Create

It will land you on the deploy page. We will come back to it in a little bit. We need a database before we host the app.

3. Setting up Heroku DB

  • Click on the resources tab
  • On the bottom next to the search bar, you will see Find more addons.
  • Click on it, and it will redirect to the add-ons page
  • To find Postgres do a Ctrl+F and search for Postgres
  • Click on Heroku Postgres
  • On the next page, click Install Postgres on the top right corner
  • Choose Hobby plan and search for your app name in the search bar
  • Click submit order form.

This will create a DB and attach it to the application we created

4. Exploring DB Settings

After completion of the above step, you will land on the resources tab. If not, open the resources tab

  • Click to open the new Postgres resource. It might take a few seconds to load
  • Click on the settings tab. It will expose the Postgres connection URL

Close the window and come back to the app window

4.1 Adding ENV Variables

  1. Go to the settings tab
  2. Click on reveal config vars
  3. You will see the DATABASE_URL key already added
  4. If you have any other env config use the same

5. Getting your Code Ready

  • Add your flask models to
  • Add your REST APIs to
  • Ensure your has the following snippet at the end. Uncommented.
  • Ensure your app runs without any error python Test all your APIs. Once it runs fine, stop the application with ctrl + C.

Next, we need to ensure that our gunicorn server works fine with all the APIs. Not applicable for windows

  • Run the app with gunicorn gunicorn run:app -b :5000
  • Check one of your APIs
  • Stop the app

6. Deploy the App - Method 1 - Using Heroku CLI

6.1 Install Heroku Cli

  1. Click on the deploy tab
  2. I hope you have installed Heroku-cli. If not time to install it -

6.2 Let's Deploy

  • On the terminal, run
heroku git:remote -a <your-herkou-app-name>
git add .
git commit -m <add a commit message>
git push heroku main

You will see Heroku building the app and Deploying the application. All of this happens seamlessly because we structured the application with a template that has

  • Procfile
  • requirements.txt

Once it is done, replace all your URLs with the Heroku Generated URL.

Redeploying application

git add <new_changes>
git commit -m "add new changes."
git push heroku main

7. Deploy the App - Method 2 - Using Github

7.1 Authorize Heroku App

Under the deploy tab, click on Connect to Github and click the button Connect to Github

  • On the screen that pops up Authorize Heroku to provide access to your Github account
  • Search for the repository and click connect

  • Click on Enable Automatic deploys.

From here on, any time you push your code to the main branch, the app will automatically deploy. You can manually deploy using Deploy from the Manual deploy section.

Checking logs

You can check the logs by clicking on the Heroku dashboard from More -> View Logs. If you use the Heroku-CLI method, check it using the following command

heroku logs --tail