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What is Flask? What is it used for?

by Snehal Naik
What is Flask and What is it used for
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Whether you are a beginner or a seasoned web developer, a set of readymade tools and resources always come in handy to build and manage applications. Web frameworks and technologies, such as Flask, Ruby on Rails, Express.js, Spring Boot, React, etc., cater to different programming languages and have their unique strengths and use cases. Web frameworks make a developer’s life easy and simple. However, it is important to choose a framework that suits your needs and requirements. Flask is among the top 12 web frameworks used by developers globally. When it comes to using Python web frameworks, Flask and Django are the two names that are often heard. So, what is Flask? What is it used for? What are its features and applications? Read on to know more.  

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Choosing the Right Framework for Web Development

As a professional developer, you know how important it is to choose the right web development framework. The framework you choose determines the efficiency, scalability, and maintainability of the web application you will build. Here are the key reasons why you should select an appropriate framework:

The framework you choose should be able to scale the application both horizontally and vertically. It should offer solutions for increased user loads and efficiently manage resources.

Productivity and Time Efficiency 
A well-designed web development framework should offer pre-built components, libraries, and tools. Built-in components can help developers save time as they reduce the need to write repetitive code from scratch.

Learning Curve and Developer Adoption 
Well-documented frameworks have relatively better learning curves, which makes it easier for developers to grasp and use them efficiently. One should choose frameworks with lower barrier entry to begin with.

Right Web Development Framework

A good web development framework offers ample security features, preferably built-in, for handling common vulnerabilities. It should also be able to keep a track record of regular updates to address emerging security threats.

Code Quality and Maintainability 
A web framework should have structured code organization and enforce best practices. This promotes cleaner, modular, and maintainable code. It also helps when projects grow in size and complexity.

Community and Support
Good web development frameworks should have active communities of developers and support. They should also have access to forums, documentation, and third-party resources. It helps developers learn, find solutions to issues, and stay updated with the best practices.

Ecosystem and Integrations 
A good framework should come with a rich ecosystem and integrations so that developers can extend the functionality of an application. In addition, a well-built framework should also allow compatibility with third-party tools, libraries, and services to improve the capabilities of the web development stack.

Flexibility and Customization 
The right framework should allow developers to adapt the framework to suit the unique requirements of a project. The framework should provide conventions for streamlined development and offer flexibility for customization.

A good framework helps to build web applications optimized for speed and resource utilization. This works in favor of projects that have applications with high traffic or resource-intensive operations.

Future Proofing 
A good web development framework should be able to build applications that are relevant and can adapt to future changes in web development trends. A good framework should be committed to ongoing development, updates, and support.

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What is Flask?

Flask is an application framework used to develop web applications for e-commerce sites, social media platforms, and more. It is a versatile, lightweight WSGI web framework written in Python. It was designed to help developers get a quick headstart while building applications and the ability to scale up to complex applications. Flask was created by Armin Ronacher and was initially released in April 2010. The latest version of Flask (3.0.0) was released in September 2023. Flask was initially released as a simple wrapper around Werkzeug and Jinja and has become one of the most popular Python web application frameworks. 

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Flask: A Microframework

Categorized as a microframework, Flask comes with a very basic setup but helps developers create web applications quickly and with minimal code. Flask uses the Werkzeug WSGI toolkit and the Jinja2 template engine.  It does not have database abstraction layer, form validation, or any other components but supports extensions that can add application features. Flask is more adaptable to different working styles than full-stack frameworks like Django.  

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Components of Flask


Werkzeug is a WSGI (Web Server Gateway Interface) utility library for Python. It acts as the foundation for many web frameworks, including Flask. Werkzeug provides essential components for handling HTTP requests and responses, routing, and other web-related tasks. 


It is the default templating engine for Flask in Python. It manages templates in a sandbox security mechanism. Jinja is fast, expressive, and extensible. Jinja allows developers to embed dynamic content and logic, and control structures directly within HTML templates. 


MarkupSafe is a valuable component of Flask’s toolkit. It is a Python library used to mark strings as “safe” for HTML escaping. Developers working with Flask use MarkupSafe to handle the proper escape of content when rendering templates. It ensures that user-generated content is properly sanitized before being displayed in HTML, which prevents Cross-Site Scripting (XSS) attacks. 


ItsDangerous is a crucial component in Flask for creating secure and tamper-proof digital signatures. It is also a Python library that helps create and verify digital signatures to securely serialize data. In Flask, it is used for tasks that require high data integrity and security, like user sessions and token generation. 

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Features of Flask

Features of Flask

Flask has some salient features that contribute to its reputation as a flexible and user-friendly web framework.

Lightweight and modular structure
Flask is a lightweight microframework with a minimalist philosophy. It does not impose a rigid structure but provides the essential components needed for web development. It lets developers choose components and libraries based on their specific project requirements. Flask thus promotes a modular and customizable approach to building web applications.

Built-in development server  
Flask’s built-in development server makes testing and debugging applications simpler for developers. The development server makes running and iterating code easy for developers, as it is easy to code and requires no additional configuration.

Jinja2 templating engine  
Jinja2 is a templating engine that Flask uses for generating dynamic HTML content in web applications. It allows developers to embed dynamic content seamlessly within HTML templates. With Jinja2, it is possible to have template inheritance, macros, and filters. This allows developers to structure and present data in a powerful and expressive way.

Werkzeug WSGI toolkit integration 
With Werkzeug, Flask can handle HTTP request and response objects, routing, and utilities. The toolkit has the essential components for building WSGI-compliant web applications. This integration helps Flask applications adhere to WSGI standards, making them compatible with various web servers and deployment scenarios.

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Advantages of Using Flask


Flask is simple and lightweight. Its lightweight design and easy syntax provide a simple structure to get a web application up and running without unnecessary complexity.


As Flask is a microframework, developers can choose which components they want to choose for a project. This makes Flask a great choice for building smaller projects and prototypes.  

Ease of Learning 

As mentioned before, Flask has a straightforward syntax, which helps even beginners to learn its essentials faster. Flask also offers clear documentation so that all developers, experienced and new, can stay updated about the framework.  

Werkzeug and Jinja2 

The integration with the Werkzeug WSGI toolkit and the Jinja2 templating engine is one of the best advantages of using Flask. Werkzeug offers utilities, and Jinja2 enables efficient and flexible template rendering, enhancing Flask’s capabilities. 

Active Community 

The support offered by the Flask developer community makes it possible for developers around the world to have a wealth of resources. Additionally, the platform also makes extensions available that can be easily integrated into Flask applications. 

Ideal for Prototyping 

It is easy to finish the setup of Flask. Hence, it is used by developers to build prototypes and develop minimal viable products (MVPs). It also allows developers to rapidly iterate and test ideas.

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Disadvantages of Flask

Limited Functionality 

Flask’s microframework feature sometimes limits its functionality. As a microframework, it only has essential features. Because of this, developers have to integrate additional libraries or switch to a more feature-rich framework when working on larger and more complex applications.

Not Opinionated

Flask does not have strong opinions on application structure. This might make development teams come up with their own conventions, which might affect the consistency across projects.  

Less Built-in Features 

Flask intentionally includes fewer built-in features compared to full-stack frameworks. This might make developers look for external libraries for their app development. 

Not Suitable for Large Projects  

Flask is a great choice for small projects, but it is a poor choice for large-scale applications with complex requirements. Larger frameworks like Django might be more suitable for such projects. 

Database Support 

Apart from SQLAlchemy, Flask offers little support for database integration. Hence, developers need to make additional decisions and configurations for database-related tasks.

Dependency on Extension 

Flask offers very little when it comes to built-in extension features. Developers have to depend on extensions that need to be managed for compatibility and potential conflicts between different components. 

Steeper Learning Curve for Complex Tasks 

Flask is a simple framework for beginners but relies on many external features. Mastering more advanced or complex tasks means that they have to familiarize themselves with many third-party extensions. This might lead to a steeper learning curve compared to more opinionated frameworks that provide built-in solutions.

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Flask Use Cases and Applications

Web application development

Developers can create dynamic and interactive web pages by combining Flask with HTML templates and integrating with databases. The applications can range from small projects to large-scale applications. Portfolio websites, social network web applications, and blog apps are some examples of Flask-based app development.  

RESTful API development  

Flask’s minimalistic design and ability to support request handling make it a great tool to build RESTful APIs (Application Programming Interfaces). Social media sites like LinkedIn, Twitter and Facebook can use REST APIs to integrate with third-party applications and allow posting updates. Developers can implement CRUD (Create, Read, Update, Delete) operations and handle HTTP requests in the apps they build with Flask.  

Flask Use Cases and Applications

Microservices architecture  

With Flask, it is possible to build applications where services are divided into small, independent components. For instance, Netflix has a microservice architecture, which makes it easy for the platform to be maintained and modulated. Further, since Flask allows extensions, applications can be integrated with other components and services within a microservices-based system. 

Educational purposes and prototyping 

The simple architecture of Flask makes it a great choice to create models that teach web development and Python programming. For instance, Real Python, an online platform offering Python tutorials and resources, has used Flask for educational content. Flask’s straightforward syntax and minimalistic structure make it easy for beginners to understand the fundamentals of web development. Also, Flask is a preferred framework for building prototypes. This allows developers to test ideas and build proof-of-concept applications before scaling to more robust frameworks.  

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Companies using Flask Worldwide

Companies using Flask Worldwide
  • Samsung 
  • Pinterest 
  • Airbnb 
  • Netflix 
  • Reddit 
  • MIT 
  • Uber 
  • Mozilla
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Flask is among the top Python frameworks used for web application development. It is popular because of its lightweight features and is a great choice for building smaller projects. Flask is used by developers worldwide to build web applications, RESTful APIs, and microservices. Its simple and modular structure makes it an easy framework to learn for beginners, compared to other full-stack frameworks like Django. It is true that it can be tedious to use Flask for big projects. However, if you have a list of tried and tested extensions that can be used with Flask, you can use the microframework for big web application projects. With a thriving community and seamless integration of powerful tools like Werkzeug and Jinja2, Flask empowers developers to rapidly build scalable and maintainable solutions.

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Flask is categorized as a microframework as it only provides essential components for web development.

Yes. Flask is a free, open-source framework under a BSD license.

Since Flask has a simple structure, it is a good choice for simple applications or microservices.

Flask’s built-in server has to be put behind a real web server to communicate with Flask through a WSGI protocol. It might not be a good idea to use it for production.

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