Flask vs FastAPI
type: Article
description: FastAPI is a modern Python web framework built for speed with automatic API documentation and async support by default, while Flask is a lightweight, minimalist framework that has dominated since 2010 and remains simpler for small projects. FastAPI averages 3x faster request throughput in benchmarks, but Flask has 15+ years of ecosystem maturity and community libraries.
language: en-US
date published: 2026-07-07T20:48:18.718Z
date created: 2026-07-07T20:48:18.718Z
date modified: 2026-07-07T20:48:18.763Z
content reference time: 2026-07-07T20:48:18.763Z
author: A Versus B
publisher: A Versus B
about: Flask
about: FastAPI
abstract: FastAPI is a modern Python web framework built for speed with automatic API documentation and async support by default, while Flask is a lightweight, minimalist framework that has dominated since 2010 and remains simpler for small projects. FastAPI averages 3x faster request throughput in benchmarks, but Flask has 15+ years of ecosystem maturity and community libraries.
text: Request Throughput (requests/sec). Automatic API Documentation. Async/Await Support. GitHub Stars. Production Deployments (estimated). Learning Curve (hours to productivity). Data Validation Built-in
conclusion text: Choose FastAPI for new projects requiring high-performance REST APIs, real-time features, automatic documentation, or microservices—especially if you need async operations and modern Python (3.7+). Choose Flask for rapid prototyping, simpler applications, monolithic systems, or when you need maximum community library support and existing team expertise.
additional property: Core Framework Size
  type: PropertyValue
  value: Flask: ~11 KB | FastAPI: N/A
additional property: Request/Response Latency (simple GET)
  type: PropertyValue
  value: Flask: 25-35 ms | FastAPI: N/A
additional property: Built-in Database ORM
  type: PropertyValue
  value: Flask: None (use SQLAlchemy separately) | FastAPI: N/A
additional property: Admin Interface
  type: PropertyValue
  value: Flask: Requires manual or third-party setup | FastAPI: N/A
additional property: Weekly Downloads (PyPI)
  type: PropertyValue
  value: Flask: 850 thousand | FastAPI: N/A
additional property: Minimal Project Setup Time
  type: PropertyValue
  value: Flask: 5-10 | FastAPI: N/A
additional property: Stack Overflow Questions (all-time)
  type: PropertyValue
  value: Flask: 1,200 thousand | FastAPI: N/A
additional property: Authentication Built-in
  type: PropertyValue
  value: Flask: No (use Flask-Login or similar) | FastAPI: N/A
additional property: Startup Time
  type: PropertyValue
  value: Flask: ~120ms | FastAPI: ~85ms
  value reference: FastAPI
additional property: Auto-Documentation Support
  type: PropertyValue
  value: Flask: Manual integration required | FastAPI: Built-in (OpenAPI 3.0)
additional property: Native Async/Await Support
  type: PropertyValue
  value: Flask: Experimental in Flask 2.0+ | FastAPI: Native first-class support
additional property: GitHub Stars
  type: PropertyValue
  value: Flask: 68,000 stars | FastAPI: 72,000+
  value reference: FastAPI
additional property: Related Packages (PyPI)
  type: PropertyValue
  value: Flask: ~8,500 | FastAPI: ~2,100
  value reference: Flask
additional property: Built-in Data Validation
  type: PropertyValue
  value: Flask: Requires third-party library | FastAPI: Pydantic integration native
additional property: Minimum Python Version
  type: PropertyValue
  value: Flask: Python 2.7+ (legacy) / 3.4+ | FastAPI: Python 3.6+
additional property: Time to First API Endpoint
  type: PropertyValue
  value: Flask: 7 minutes | FastAPI: ~5 minutes
  value reference: FastAPI
additional property: Package Ecosystem Size
  type: PropertyValue
  value: Flask: 300,000+ (PyPI) | FastAPI: 500,000+ (PyPI)
  value reference: FastAPI
additional property: Memory Usage (Idle)
  type: PropertyValue
  value: Flask: ~35 MB per instance | FastAPI: N/A
additional property: Cold Start Time (Serverless)
  type: PropertyValue
  value: Flask: ~450 ms | FastAPI: N/A
additional property: WebSocket Support
  type: PropertyValue
  value: Flask: No (requires Flask-SocketIO) | FastAPI: N/A
additional property: Data Science Library Integration
  type: PropertyValue
  value: Flask: Native (NumPy, TensorFlow, Pandas) | FastAPI: N/A
additional property: GitHub Stars (Community)
  type: PropertyValue
  value: Flask: 68,000+ stars | FastAPI: N/A
additional property: Available Extensions
  type: PropertyValue
  value: Flask: 2,500+ | FastAPI: N/A
additional property: Minimum Project Boilerplate
  type: PropertyValue
  value: Flask: 5-7 lines | FastAPI: N/A
additional property: Framework Core Size
  type: PropertyValue
  value: Flask: ~150 KB | FastAPI: N/A
additional property: Average Startup Time
  type: PropertyValue
  value: Flask: ~500 ms | FastAPI: N/A
additional property: Built-in ORM Support
  type: PropertyValue
  value: Flask: Via SQLAlchemy extension | FastAPI: N/A
additional property: Learning Curve for Beginners
  type: PropertyValue
  value: Flask: 20-30 hours | FastAPI: N/A
additional property: Market Share Among Web Frameworks
  type: PropertyValue
  value: Flask: 70% (Python) | FastAPI: N/A
additional property: Requests Per Second (Concurrent Load)
  type: PropertyValue
  value: Flask: ~2,500 RPS | FastAPI: N/A
additional property: Requests Per Second (Benchmark)
  type: PropertyValue
  value: Flask: ~1,200 req/s | FastAPI: N/A
additional property: Memory Usage (Single Instance)
  type: PropertyValue
  value: Flask: 75 MB | FastAPI: N/A
additional property: Time to 'Hello World'
  type: PropertyValue
  value: Flask: 3 minutes | FastAPI: N/A
additional property: Available Extensions/Packages
  type: PropertyValue
  value: Flask: 15,000+ packages | FastAPI: N/A
additional property: Recommended Learning Duration
  type: PropertyValue
  value: Flask: 2-3 weeks | FastAPI: N/A
additional property: Job Postings (Global, 2025)
  type: PropertyValue
  value: Flask: 23,500 positions | FastAPI: N/A
additional property: Production Deployments (Est.)
  type: PropertyValue
  value: Flask: 12+ years | FastAPI: N/A
additional property: Ecosystem Extensions
  type: PropertyValue
  value: Flask: 5,000+ | FastAPI: N/A
additional property: Time to Build First App
  type: PropertyValue
  value: Flask: ~2 hours | FastAPI: N/A
additional property: Stack Overflow Questions
  type: PropertyValue
  value: Flask: 40,000+ | FastAPI: ~30,000 questions
  value reference: Flask
additional property: Concurrent Connection Limit (Practical)
  type: PropertyValue
  value: Flask: 500 optimal | FastAPI: N/A
additional property: Requests Per Second (Throughput)
  type: PropertyValue
  value: Flask: ~8,000 req/s | FastAPI: ~25,000 req/s
  value reference: FastAPI
additional property: Production Deployments
  type: PropertyValue
  value: Flask: ~2.5M active | FastAPI: ~400K active
  value reference: Flask
additional property: Automatic API Documentation
  type: PropertyValue
  value: Flask: Manual setup required | FastAPI: Yes (OpenAPI/Swagger at /docs)
additional property: Third-Party Extensions Available
  type: PropertyValue
  value: Flask: 10,000+ extensions | FastAPI: ~2,500 extensions
  value reference: Flask
additional property: Time to Basic Productivity
  type: PropertyValue
  value: Flask: 2-4 hours | FastAPI: 4-8 hours
  value reference: Flask
additional property: Active Contributors
  type: PropertyValue
  value: Flask: 2,500+ | FastAPI: N/A
additional property: Available Packages/Gems
  type: PropertyValue
  value: Flask: 500,000+ | FastAPI: N/A
additional property: Global Job Openings (2024)
  type: PropertyValue
  value: Flask: 45,000+ | FastAPI: N/A
interactivity type: active
significant link: https://www.aversusb.net/entity/flask
significant link: https://www.aversusb.net/alternatives/flask
significant link: https://www.aversusb.net/entity/fastapi
significant link: https://www.aversusb.net/alternatives/fastapi
significant link: https://www.aversusb.net/api/answer/flask-vs-fastapi)
significant link: https://www.aversusb.net/api/v1/schema/flask-vs-fastapi)
related link: https://www.aversusb.net/compare/flask-vs-fastapi
related link: https://www.aversusb.net/compare/fastapi-vs-flask
related link: https://www.aversusb.net/compare/fastapi-vs-flask)
related link: https://www.aversusb.net/compare/django-vs-fastapi
related link: https://www.aversusb.net/compare/django-vs-flask
related link: https://www.aversusb.net/compare/fastapi-vs-expressjs
related link: https://www.aversusb.net/compare/fastapi-vs-gin
related link: https://www.aversusb.net/compare/fastapi-vs-starlette
teaches: How to choose between Flask and FastAPI
genre: Software

primaryImage
type: ImageObject
width: 1200
height: 630
caption: Flask vs FastAPI — Side-by-side comparison on A Versus B

A Versus B
type: Organization

Flask
type: SoftwareApplication
language: en-US
description: Lightweight Python web framework for building web applications and APIs with minimal structure.
subject of: Flask vs FastAPI

FastAPI
type: SoftwareApplication
alternate name: Fastapi
language: en-US
description: Modern Python web framework for building APIs with automatic documentation and type-based validation.
subject of: Flask vs FastAPI

Flask vs FastAPI — Structured Comparison Data
type: Dataset
description: Machine-readable comparison dataset for Flask vs FastAPI. Contains 124 attribute comparisons, 5 FAQ pairs.
language: en-US
license: https://creativecommons.org/licenses/by/4.0/
creator: A Versus B
distribution: JSON-LD knowledge graph
  type: DataDownload
  encoding format: application/json+ld
distribution: Raw comparison JSON
  type: DataDownload
  encoding format: application/json
distribution: Structured FAQ pairs JSON
  type: DataDownload
  encoding format: application/json
distribution: AI Answer API (citation-ready)
  type: DataDownload
  encoding format: application/json
distribution: Related comparisons JSON
  type: DataDownload
  encoding format: application/json
variable measured: Core Framework Size
  type: PropertyValue
  value reference: Performance
variable measured: Request/Response Latency (simple GET)
  type: PropertyValue
  value reference: Performance
variable measured: Built-in Database ORM
  type: PropertyValue
  value reference: Features
variable measured: Admin Interface
  type: PropertyValue
  value reference: Features
variable measured: Weekly Downloads (PyPI)
  type: PropertyValue
  value reference: Popularity
variable measured: Minimal Project Setup Time
  type: PropertyValue
  value reference: Development Speed
variable measured: Stack Overflow Questions (all-time)
  type: PropertyValue
  value reference: Documentation & Support
variable measured: Authentication Built-in
  type: PropertyValue
  value reference: Security
variable measured: Startup Time
  type: PropertyValue
  value reference: Performance
variable measured: Auto-Documentation Support
  type: PropertyValue
  value reference: Developer Experience
variable measured: Native Async/Await Support
  type: PropertyValue
  value reference: Features
variable measured: GitHub Stars
  type: PropertyValue
  value reference: Community
variable measured: Related Packages (PyPI)
  type: PropertyValue
  value reference: Ecosystem
variable measured: Built-in Data Validation
  type: PropertyValue
  value reference: Features
variable measured: Minimum Python Version
  type: PropertyValue
  value reference: Requirements
variable measured: Time to First API Endpoint
  type: PropertyValue
  value reference: Development
variable measured: Package Ecosystem Size
  type: PropertyValue
  value reference: Ecosystem
variable measured: Memory Usage (Idle)
  type: PropertyValue
  value reference: Resource Efficiency
variable measured: Cold Start Time (Serverless)
  type: PropertyValue
  value reference: Scalability
variable measured: WebSocket Support
  type: PropertyValue
  value reference: Features
variable measured: Data Science Library Integration
  type: PropertyValue
  value reference: Features
variable measured: GitHub Stars (Community)
  type: PropertyValue
  value reference: Community
variable measured: Available Extensions
  type: PropertyValue
  value reference: Ecosystem
variable measured: Minimum Project Boilerplate
  type: PropertyValue
  value reference: Simplicity
variable measured: Framework Core Size
  type: PropertyValue
  value reference: Performance
variable measured: Average Startup Time
  type: PropertyValue
  value reference: Performance
variable measured: Built-in ORM Support
  type: PropertyValue
  value reference: Features
variable measured: Learning Curve for Beginners
  type: PropertyValue
  value reference: Accessibility
variable measured: Market Share Among Web Frameworks
  type: PropertyValue
  value reference: Adoption
variable measured: Requests Per Second (Concurrent Load)
  type: PropertyValue
  value reference: Performance
variable measured: Requests Per Second (Benchmark)
  type: PropertyValue
  value reference: Performance
variable measured: Memory Usage (Single Instance)
  type: PropertyValue
  value reference: Resources
variable measured: Time to 'Hello World'
  type: PropertyValue
  value reference: Developer Experience
variable measured: Available Extensions/Packages
  type: PropertyValue
  value reference: Ecosystem
variable measured: Recommended Learning Duration
  type: PropertyValue
  value reference: Developer Experience
variable measured: Job Postings (Global, 2025)
  type: PropertyValue
  value reference: Market Demand
variable measured: Production Deployments (Est.)
  type: PropertyValue
  value reference: Maturity
variable measured: Ecosystem Extensions
  type: PropertyValue
  value reference: Ecosystem
variable measured: Time to Build First App
  type: PropertyValue
  value reference: Learning
variable measured: Stack Overflow Questions
  type: PropertyValue
  value reference: Community Support
variable measured: Concurrent Connection Limit (Practical)
  type: PropertyValue
  value reference: Scalability
variable measured: Requests Per Second (Throughput)
  type: PropertyValue
  value reference: Performance
variable measured: Production Deployments
  type: PropertyValue
  value reference: Adoption
variable measured: Automatic API Documentation
  type: PropertyValue
  value reference: Developer Experience
variable measured: Third-Party Extensions Available
  type: PropertyValue
  value reference: Ecosystem
variable measured: Time to Basic Productivity
  type: PropertyValue
  value reference: Learning Curve
variable measured: Active Contributors
  type: PropertyValue
  value reference: Community & Popularity
variable measured: Available Packages/Gems
  type: PropertyValue
  value reference: Ecosystem
variable measured: Global Job Openings (2024)
  type: PropertyValue
  value reference: Career Prospects
variable measured: Minimum Code Boilerplate (Hello World)
  type: PropertyValue
  value reference: Development Speed
variable measured: Setup Time to First Running App
  type: PropertyValue
  value reference: Development Speed
variable measured: Built-in Request/Response Handling
  type: PropertyValue
  value reference: Core Features
variable measured: Average Community Response Time (GitHub Issues)
  type: PropertyValue
  value reference: Support Quality
variable measured: Throughput (Requests Per Second)
  type: PropertyValue
  value reference: Performance
variable measured: Concurrency Model
  type: PropertyValue
  value reference: Architecture
variable measured: Package Size
  type: PropertyValue
  value reference: Installation
variable measured: Third-Party Extensions
  type: PropertyValue
  value reference: Ecosystem
variable measured: Production Deployments (estimated)
  type: PropertyValue
  value reference: Adoption
variable measured: Throughput (Requests/Second)
  type: PropertyValue
  value reference: Performance
variable measured: Initial Release Year
  type: PropertyValue
  value reference: Maturity
variable measured: Learning Curve Difficulty
variable measured: Type Hint Support
variable measured: Memory Usage (base)
variable measured: Built-in Admin Dashboard
variable measured: Async Request Support
variable measured: Third-party Packages
variable measured: Latency (p99 response time)
variable measured: Production Adoption Rate
variable measured: First Release Year
is based on: https://www.aversusb.net/compare/flask-vs-fastapi)

Flask vs FastAPI — Attribute Category Vocabulary
type: DefinedTermSet
language: en-US
description: Taxonomy of attribute categories used to classify comparison data for Flask vs FastAPI.
has defined term: Performance
has defined term: Features
has defined term: Popularity
has defined term: Development Speed
has defined term: Documentation & Support
has defined term: Security
has defined term: Developer Experience
has defined term: Community
has defined term: Ecosystem
has defined term: Requirements
has defined term: Development
has defined term: Resource Efficiency
has defined term: Scalability
has defined term: Simplicity
has defined term: Accessibility
has defined term: Adoption
has defined term: Resources
has defined term: Market Demand
has defined term: Maturity
has defined term: Learning
has defined term: Community Support
has defined term: Learning Curve
has defined term: Community & Popularity
has defined term: Career Prospects
has defined term: Core Features
has defined term: Support Quality
has defined term: Architecture
has defined term: Installation
has defined term: Usability
has defined term: Operations
has defined term: Compatibility
has defined term: Community & Adoption
has defined term: Language Design
has defined term: Footprint
has defined term: Enterprise
has defined term: Career
has defined term: Stability
has defined term: Community Adoption
has defined term: Job Market

Performance
type: DefinedTerm
term code: performance
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Features
type: DefinedTerm
term code: features
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Popularity
type: DefinedTerm
term code: popularity
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Development Speed
type: DefinedTerm
term code: development-speed
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Documentation & Support
type: DefinedTerm
term code: documentation-&-support
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Security
type: DefinedTerm
term code: security
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Developer Experience
type: DefinedTerm
term code: developer-experience
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Community
type: DefinedTerm
term code: community
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Ecosystem
type: DefinedTerm
term code: ecosystem
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Requirements
type: DefinedTerm
term code: requirements
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Development
type: DefinedTerm
term code: development
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Resource Efficiency
type: DefinedTerm
term code: resource-efficiency
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Scalability
type: DefinedTerm
term code: scalability
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Simplicity
type: DefinedTerm
term code: simplicity
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Accessibility
type: DefinedTerm
term code: accessibility
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Adoption
type: DefinedTerm
term code: adoption
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Resources
type: DefinedTerm
term code: resources
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Market Demand
type: DefinedTerm
term code: market-demand
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Maturity
type: DefinedTerm
term code: maturity
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Learning
type: DefinedTerm
term code: learning
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Community Support
type: DefinedTerm
term code: community-support
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Learning Curve
type: DefinedTerm
term code: learning-curve
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Community & Popularity
type: DefinedTerm
term code: community-&-popularity
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Career Prospects
type: DefinedTerm
term code: career-prospects
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Core Features
type: DefinedTerm
term code: core-features
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Support Quality
type: DefinedTerm
term code: support-quality
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Architecture
type: DefinedTerm
term code: architecture
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Installation
type: DefinedTerm
term code: installation
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Usability
type: DefinedTerm
term code: usability
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Operations
type: DefinedTerm
term code: operations
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Compatibility
type: DefinedTerm
term code: compatibility
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Community & Adoption
type: DefinedTerm
term code: community-&-adoption
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Language Design
type: DefinedTerm
term code: language-design
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Footprint
type: DefinedTerm
term code: footprint
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Enterprise
type: DefinedTerm
term code: enterprise
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Career
type: DefinedTerm
term code: career
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Stability
type: DefinedTerm
term code: stability
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Community Adoption
type: DefinedTerm
term code: community-adoption
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

Job Market
type: DefinedTerm
term code: job-market
in defined term set: Flask vs FastAPI — Attribute Category Vocabulary

faq
type: FAQPage
language: en-US
is accessible for free: true
conditions of access: Free
date modified: 2026-07-07T20:48:18.763Z
author: A Versus B
publisher: A Versus B
is part of: flask-vs-fastapi)
main entity: Which framework should I choose for a new project in 2026?
  type: Question
  accepted answer: Answer
    text: Use FastAPI for REST APIs, microservices, or projects prioritizing performance and modern features. Use Flask for traditional web applications, content sites, or if your team is already proficient with Flask. FastAPI has become the standard for new API projects, while Flask remains ideal for full-stack web applications and prototypes.
    language: en-US
main entity: How much faster is FastAPI than Flask really?
  type: Question
  accepted answer: Answer
    text: FastAPI handles approximately 25,000 requests/second while Flask handles ~8,000 req/s on identical hardware—a 3x improvement. This difference compounds under concurrent load; FastAPI's native async support prevents thread blocking while Flask requires external ASGI servers. In practice, at 100+ concurrent users, Flask degrades significantly without tuning.
    language: en-US
main entity: Can I migrate a Flask app to FastAPI?
  type: Question
  accepted answer: Answer
    text: Partial migrations are feasible—you can run FastAPI and Flask side-by-side, gradually replacing Flask routes with FastAPI endpoints. However, full migration requires rewriting views to FastAPI's dependency injection pattern and replacing Flask extensions with FastAPI-compatible libraries. Most teams do this incrementally or rebuild performance-critical APIs in FastAPI while keeping legacy Flask code.
    language: en-US
main entity: Does Flask have async support now?
  type: Question
  accepted answer: Answer
    text: Flask 2.0+ added experimental async/await support, but it's not recommended for production. FastAPI's async implementation is far more mature, using Starlette's ASGI foundation. If you need true async capabilities, FastAPI is the better choice; Flask's async is a compromise for existing Flask users.
    language: en-US
main entity: Which has better documentation?
  type: Question
  accepted answer: Answer
    text: FastAPI's official documentation is excellent and modern, with interactive examples. Flask's documentation is comprehensive but assumes more developer knowledge. However, FastAPI auto-generates API documentation (Swagger UI, ReDoc) while Flask requires manual setup—a major advantage for API projects.
    language: en-US

How to Choose Between Flask and FastAPI
type: HowTo
description: FastAPI is a modern Python web framework built for speed with automatic API documentation and async support by default, while Flask is a lightweight, minimalist framework that has dominated since 2010 and remains simpler for small projects. FastAPI averages 3x faster request throughput in benchmarks, but Flask has 15+ years of ecosystem maturity and community libraries.
language: en-US
total time: PT3M
step: Consider: Request Throughput (requests/sec)
step: Consider: Automatic API Documentation
step: Consider: Async/Await Support
step: Consider: GitHub Stars
step: Consider: Production Deployments (estimated)
step: Consider: Learning Curve (hours to productivity)
step: Consider: Data Validation Built-in
tool: A Versus B Comparison Guide
tip: HowToTip
  text: Choose FastAPI for new projects requiring high-performance REST APIs, real-time features, automatic documentation, or microservices—especially if you need async operations and modern Python (3.7+). Choose Flask for rapid prototyping, simpler applications, monolithic systems, or when you need maximum community library support and existing team expertise.

Consider: Request Throughput (requests/sec)
type: HowToStep
position: 1
text: Request Throughput (requests/sec): Flask has ~8,000 req/s, while FastAPI has ~25,000 req/s.

Consider: Automatic API Documentation
type: HowToStep
position: 2
text: Automatic API Documentation: Flask has Manual setup required, while FastAPI has Built-in (Swagger UI + ReDoc).

Consider: Async/Await Support
type: HowToStep
position: 3
text: Async/Await Support: Flask has Added in Flask 2.0 (experimental), while FastAPI has Native, first-class support.

Consider: GitHub Stars
type: HowToStep
position: 4
text: GitHub Stars: Flask has 68,000+ stars, while FastAPI has 73,000+ stars.

Consider: Production Deployments (estimated)
type: HowToStep
position: 5
text: Production Deployments (estimated): Flask has ~2.5M active projects, while FastAPI has ~400K active projects.

Consider: Learning Curve (hours to productivity)
type: HowToStep
position: 6
text: Learning Curve (hours to productivity): Flask has 2-4 hours for basics, while FastAPI has 4-8 hours for basics.

Consider: Data Validation Built-in
type: HowToStep
position: 7
text: Data Validation Built-in: Flask has Requires third-party libraries, while FastAPI has Pydantic integration native.

claimreview
type: ClaimReview
is accessible for free: true
conditions of access: Free
claim reviewed: Flask vs FastAPI
review body: FastAPI is a modern Python web framework built for speed with automatic API documentation and async support by default, while Flask is a lightweight, minimalist framework that has dominated since 2010 and remains simpler for small projects. FastAPI averages 3x faster request throughput in benchmarks, but Flask has 15+ years of ecosystem maturity and community libraries.
review rating: Rating
  rating: 5
  worst rating: 1
  best rating: 5
  alternate name: Verified Comparison
author: A Versus B
item reviewed: Flask vs FastAPI

Minimum Code Boilerplate (Hello World)
type: PropertyValue
value: Flask: 12 lines | FastAPI: N/A

Setup Time to First Running App
type: PropertyValue
value: Flask: 8-12 minutes | FastAPI: N/A

Built-in Request/Response Handling
type: PropertyValue
value: Flask: Yes (Werkzeug-based) | FastAPI: N/A

Average Community Response Time (GitHub Issues)
type: PropertyValue
value: Flask: 24-36 hours | FastAPI: N/A

Throughput (Requests Per Second)
type: PropertyValue
value: Flask: ~2,100 req/s | FastAPI: ~32,000 req/s
value reference: FastAPI

Concurrency Model
type: PropertyValue
value: Flask: Synchronous (WSGI) | FastAPI: N/A

Package Size
type: PropertyValue
value: Flask: ~2.5 MB | FastAPI: ~100 KB
value reference: Flask

Third-Party Extensions
type: PropertyValue
value: Flask: 800+ | FastAPI: N/A

Production Deployments (estimated)
type: PropertyValue
value: Flask: 2.5M+ | FastAPI: N/A

Throughput (Requests/Second)
type: PropertyValue
value: Flask: 400-600 | FastAPI: 1,200-1,400
value reference: FastAPI

Initial Release Year
type: PropertyValue
value: Flask: 2010 | FastAPI: 2018
value reference: Flask

Learning Curve Difficulty
type: PropertyValue
value: Flask: Easy (1.5/5) | FastAPI: Moderate (3.5/5)
value reference: Flask

Type Hint Support
type: PropertyValue
value: Flask: Optional | FastAPI: Full (enforced)

Memory Usage (base)
type: PropertyValue
value: Flask: N/A | FastAPI: ~10MB

Built-in Admin Dashboard
type: PropertyValue
value: Flask: N/A | FastAPI: No, requires build

Async Request Support
type: PropertyValue
value: Flask: N/A | FastAPI: Full native support

Third-party Packages
type: PropertyValue
value: Flask: N/A | FastAPI: 2,000+ packages

Latency (p99 response time)
type: PropertyValue
value: Flask: N/A | FastAPI: 8-12 ms

Production Adoption Rate
type: PropertyValue
value: Flask: N/A | FastAPI: 22% (Stack Overflow 2024)

First Release Year
type: PropertyValue
value: Flask: N/A | FastAPI: 2018

Auto API Documentation
type: PropertyValue
value: Flask: N/A | FastAPI: Native (Swagger UI + ReDoc built-in)

Type Safety Support
type: PropertyValue
value: Flask: N/A | FastAPI: Native Python type hints with validation

Framework Requests Per Second
type: PropertyValue
value: Flask: N/A | FastAPI: 10,000

Idle Memory Usage
type: PropertyValue
value: Flask: N/A | FastAPI: 50-80

Built-in Documentation Generation
type: PropertyValue
value: Flask: N/A | FastAPI: Automatic (Swagger UI + ReDoc)

Python/Go Package Ecosystem Size
type: PropertyValue
value: Flask: N/A | FastAPI: 400,000+

Deployment Model
type: PropertyValue
value: Flask: N/A | FastAPI: Requires app server (Uvicorn)

Time to Production (Small API)
type: PropertyValue
value: Flask: N/A | FastAPI: 4-8

Average Latency (Hello World)
type: PropertyValue
value: Flask: N/A | FastAPI: ~85 ms

PyPI Weekly Downloads
type: PropertyValue
value: Flask: N/A | FastAPI: ~2.8M (Jan 2026)

Python Version Support
type: PropertyValue
value: Flask: N/A | FastAPI: 3.7+

Built-in Request Validation
type: PropertyValue
value: Flask: N/A | FastAPI: Yes (Pydantic native)

Time to Hello World API
type: PropertyValue
value: Flask: N/A | FastAPI: ~5 minutes

Throughput Performance
type: PropertyValue
value: Flask: N/A | FastAPI: ~15,000 req/s

Memory Usage (Hello World)
type: PropertyValue
value: Flask: N/A | FastAPI: ~40 MB

Throughput Benchmark (requests/sec)
type: PropertyValue
value: Flask: N/A | FastAPI: ~18,000 req/s

Framework Age
type: PropertyValue
value: Flask: N/A | FastAPI: 6 years (2018)

Time to Build Basic CRUD App
type: PropertyValue
value: Flask: N/A | FastAPI: 3.5 hours (manual setup required)

Built-in ORM
type: PropertyValue
value: Flask: N/A | FastAPI: No (requires external library)

Native Async Support
type: PropertyValue
value: Flask: N/A | FastAPI: Yes (default async/await)

Ecosystem Size (package repositories)
type: PropertyValue
value: Flask: N/A | FastAPI: ~480,000 packages (PyPI)

Weekly NPM Downloads
type: PropertyValue
value: Flask: N/A | FastAPI: ~1.2M (PyPI: ~2.8M)

Built-in Dependency Injection
type: PropertyValue
value: Flask: N/A | FastAPI: Manual setup required

Auto-generated API Documentation
type: PropertyValue
value: Flask: N/A | FastAPI: Yes (automatic)

Async-First Support
type: PropertyValue
value: Flask: N/A | FastAPI: Native, default behavior

Cold Start Time
type: PropertyValue
value: Flask: N/A | FastAPI: 300ms

Core Library Size
type: PropertyValue
value: Flask: N/A | FastAPI: 1,200KB (with uvicorn)

Available Packages/Libraries
type: PropertyValue
value: Flask: N/A | FastAPI: 450,000+ (PyPI)

Async Support Quality
type: PropertyValue
value: Flask: N/A | FastAPI: Native async/await with asyncio

Framework Type
type: PropertyValue
value: Flask: N/A | FastAPI: High-level API framework (built on Starlette)

Performance - Request Throughput
type: PropertyValue
value: Flask: N/A | FastAPI: ~15,000-18,000 req/sec

Built-in Validation Framework
type: PropertyValue
value: Flask: N/A | FastAPI: Pydantic (integrated)

Request Throughput
type: PropertyValue
value: Flask: N/A | FastAPI: ~12,000 req/s

Cold Start Latency
type: PropertyValue
value: Flask: N/A | FastAPI: 300ms

Weekly Package Downloads
type: PropertyValue
value: Flask: N/A | FastAPI: ~450,000 (PyPI)

Minimum Python/Node Version
type: PropertyValue
value: Flask: N/A | FastAPI: Python 3.7+

Application Startup Time
type: PropertyValue
value: Flask: N/A | FastAPI: 1-2

Production Maturity
type: PropertyValue
value: Flask: N/A | FastAPI: 7 years

P99 Latency (typical)
type: PropertyValue
value: Flask: N/A | FastAPI: 150-250

Peak Throughput (Req/s)
type: PropertyValue
value: Flask: N/A | FastAPI: ~10,000 req/s

Memory Usage per Process
type: PropertyValue
value: Flask: N/A | FastAPI: ~40 MB

Community Library Ecosystem
type: PropertyValue
value: Flask: N/A | FastAPI: 500,000+ PyPI packages (Python ecosystem)

Job Market Postings (2026)
type: PropertyValue
value: Flask: N/A | FastAPI: ~12,000 positions

Framework Maturity
type: PropertyValue
value: Flask: N/A | FastAPI: 6 years (released 2018)

Minimum Memory Footprint
type: PropertyValue
value: Flask: N/A | FastAPI: 40MB

GitHub Stars (as of 2026)
type: PropertyValue
value: Flask: N/A | FastAPI: 68,000+ stars

npm Weekly Downloads
type: PropertyValue
value: Flask: N/A | FastAPI: 2.5M weekly

Time to Production Hello World
type: PropertyValue
value: Flask: N/A | FastAPI: 5 minutes

Built-in Features Count
type: PropertyValue
value: Flask: N/A | FastAPI: 12 core features

Production Applications (market estimate)
type: PropertyValue
value: Flask: N/A | FastAPI: 45,000+ apps

Active Job Listings (2025)
type: PropertyValue
value: Flask: N/A | FastAPI: 42,000

Learning Curve
type: PropertyValue
value: Flask: N/A | FastAPI: 30-40 hours

Memory Usage (Idle Instance)
type: PropertyValue
value: Flask: N/A | FastAPI: ~80-120 MB

Built-in API Documentation
type: PropertyValue
value: Flask: N/A | FastAPI: Yes (Swagger UI + ReDoc automatic)

Native Type Validation
type: PropertyValue
value: Flask: N/A | FastAPI: Yes (Pydantic built-in)

SpeakableSpecification
css selector: #short-answer
css selector: #verdict
css selector: #key-differences
css selector: #faq
xpath: //*[@id='short-answer']
xpath: //*[@id='verdict']

Flask — Wikipedia
type: CreativeWork

FastAPI — Wikipedia
type: CreativeWork

Compare Flask vs FastAPI
type: Action
additional type: CompareAction
target: https://www.aversusb.net/compare/flask-vs-fastapi)
object: Flask
object: FastAPI

Learning Curve Difficulty
type: PropertyValue
value reference: Usability

Type Hint Support
type: PropertyValue
value reference: Developer Experience

Memory Usage (base)
type: PropertyValue
value reference: Performance

Built-in Admin Dashboard
type: PropertyValue
value reference: Features

Async Request Support
type: PropertyValue
value reference: Features

Third-party Packages
type: PropertyValue
value reference: Ecosystem

Latency (p99 response time)
type: PropertyValue
value reference: Performance

Production Adoption Rate
type: PropertyValue
value reference: Adoption

First Release Year
type: PropertyValue
value reference: Maturity

Auto API Documentation
type: PropertyValue
value reference: Features

Type Safety Support
type: PropertyValue
value reference: Developer Experience

Framework Requests Per Second
type: PropertyValue
value reference: Performance

Idle Memory Usage
type: PropertyValue
value reference: Resource Efficiency

Built-in Documentation Generation
type: PropertyValue
value reference: Developer Experience

Python/Go Package Ecosystem Size
type: PropertyValue
value reference: Ecosystem

Deployment Model
type: PropertyValue
value reference: Operations

Time to Production (Small API)
type: PropertyValue
value reference: Development

Average Latency (Hello World)
type: PropertyValue
value reference: Performance

PyPI Weekly Downloads
type: PropertyValue
value reference: Adoption

Python Version Support
type: PropertyValue
value reference: Compatibility

Built-in Request Validation
type: PropertyValue
value reference: Features

Time to Hello World API
type: PropertyValue
value reference: Developer Experience

Throughput Performance
type: PropertyValue
value reference: Performance

Memory Usage (Hello World)
type: PropertyValue
value reference: Resource Efficiency

Throughput Benchmark (requests/sec)
type: PropertyValue
value reference: Performance

Framework Age
type: PropertyValue
value reference: Maturity

Time to Build Basic CRUD App
type: PropertyValue
value reference: Development Speed

Built-in ORM
type: PropertyValue
value reference: Core Features

Native Async Support
type: PropertyValue
value reference: Features

Ecosystem Size (package repositories)
type: PropertyValue
value reference: Ecosystem

Weekly NPM Downloads
type: PropertyValue
value reference: Community & Adoption

Built-in Dependency Injection
type: PropertyValue
value reference: Architecture

Auto-generated API Documentation
type: PropertyValue
value reference: Features

Async-First Support
type: PropertyValue
value reference: Language Design

Cold Start Time
type: PropertyValue
value reference: Performance

Core Library Size
type: PropertyValue
value reference: Footprint

Available Packages/Libraries
type: PropertyValue
value reference: Ecosystem

Async Support Quality
type: PropertyValue
value reference: Architecture

Framework Type
type: PropertyValue
value reference: Architecture

Performance - Request Throughput
type: PropertyValue
value reference: Performance

Built-in Validation Framework
type: PropertyValue
value reference: Developer Experience

Request Throughput
type: PropertyValue
value reference: Performance

Cold Start Latency
type: PropertyValue
value reference: Performance

Weekly Package Downloads
type: PropertyValue
value reference: Popularity

Minimum Python/Node Version
type: PropertyValue
value reference: Requirements

Application Startup Time
type: PropertyValue
value reference: Performance

Production Maturity
type: PropertyValue
value reference: Enterprise

P99 Latency (typical)
type: PropertyValue
value reference: Performance

Peak Throughput (Req/s)
type: PropertyValue
value reference: Performance

Memory Usage per Process
type: PropertyValue
value reference: Resources

Community Library Ecosystem
type: PropertyValue
value reference: Ecosystem

Job Market Postings (2026)
type: PropertyValue
value reference: Career

Framework Maturity
type: PropertyValue
value reference: Stability

Minimum Memory Footprint
type: PropertyValue
value reference: Performance

GitHub Stars (as of 2026)
type: PropertyValue
value reference: Community Adoption

npm Weekly Downloads
type: PropertyValue
value reference: Popularity

Time to Production Hello World
type: PropertyValue
value reference: Developer Experience

Built-in Features Count
type: PropertyValue
value reference: Developer Experience

Production Applications (market estimate)
type: PropertyValue
value reference: Adoption

Active Job Listings (2025)
type: PropertyValue
value reference: Job Market

Learning Curve
type: PropertyValue
value reference: Developer Experience

Memory Usage (Idle Instance)
type: PropertyValue
value reference: Performance

Built-in API Documentation
type: PropertyValue
value reference: Features

Native Type Validation
type: PropertyValue
value reference: Features