software
FastAPI vs Flask 2026: Performance & Features Compared
FastAPI is a modern Python web framework built on Starlette that prioritizes speed and automatic API documentation with async support by default, while Flask is a lightweight, minimalist framework that emphasizes simplicity and flexibility with synchronous request handling. FastAPI's built-in features result in ~3x faster request handling and automatic OpenAPI/Swagger documentation, whereas Flask requires manual setup for these capabilities.
F
FastAPI
Modern high-performance Python web framework with automatic API documentation and async support.
Teams building production REST APIs, microservices, real-time applications, or systems requiring high concurrency and automatic API documentation.
Score71%
VS
F
Flask
Lightweight, minimalist Python web framework emphasizing simplicity and flexibility.
Beginners learning web development, small projects, teams preferring simplicity over performance, or applications where flexibility and minimal dependencies are priorities.
Score71%
Quick Answer
AI SummaryFastAPI is a modern Python web framework built on Starlette that prioritizes speed and automatic API documentation with async support by default, while Flask is a lightweight, minimalist framework that emphasizes simplicity and flexibility with synchronous request handling. FastAPI's built-in features result in ~3x faster request handling and automatic OpenAPI/Swagger documentation, whereas Flask requires manual setup for these capabilities.
Our Verdict
AI-assistedChoose FastAPI if you're building modern REST APIs that require high performance, automatic documentation, async operations, or type safety with built-in validation—ideal for microservices, real-time applications, and teams prioritizing developer experience. Choose Flask if you prioritize simplicity, have an existing codebase, need a lightweight framework for small projects, or prefer minimal dependencies and maximum flexibility in architecture decisions.
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F
FastAPI
6.3/10
Flask
8.7/10
F
F
Choose FastAPI if
Teams building production REST APIs, microservices, real-time applications, or systems requiring high concurrency and automatic API documentation.
F
Choose Flask if
Best pickBeginners learning web development, small projects, teams preferring simplicity over performance, or applications where flexibility and minimal dependencies are priorities.
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Key Differences at a Glance
- Request Performance (requests/sec):✓ FastAPI wins(~12,000 req/s vs ~4,000 req/s)
- Async/Await Support:✓ FastAPI wins(Native, built-in by default vs Limited, requires external libraries)
- Automatic API Documentation:✓ FastAPI wins(OpenAPI/Swagger auto-generated vs Manual setup required)
Key Facts & Figures
105 numeric metrics compared
| Metric | FastAPI | Flask | Ratio |
|---|---|---|---|
| Time to First API (Learning Curve)(hours) | 15-25 hours | 5-10 hours | |
| Core Framework Size(KB) | ~300 KB | ~60 KB | |
| Time Since Initial Release(years) | 4 years (2021) | 18 years (2010) | |
| Throughput (Requests/Second)(req/s) | 8,000-12,000 | 400-600 | |
| Startup Time(milliseconds) | 250-500ms | ~150ms | |
| Memory Usage (base)(MB) | ~10MB | — | — |
| Time to First API Endpoint(minutes) | ~5 minutes | 7 minutes | |
| Third-party Packages(packages) | 2,000+ packages | — | — |
| Latency (p99 response time)(ms) | 8-12 ms | — | — |
| Package Ecosystem Size(packages) | 500,000+ (PyPI) | 300,000+ (PyPI) | |
| Production Adoption Rate(percent) | 22% (Stack Overflow 2024) | — | — |
| First Release Year | 2018 | — | — |
| Related Packages (PyPI)(packages) | ~2,100 | ~8,500 | |
| Framework Requests Per Second(req/s) | 10,000 | — | — |
| Idle Memory Usage(MB) | 50-80 | — | — |
| Python/Go Package Ecosystem Size(packages) | 400,000+ | — | — |
| Time to Production (Small API)(hours) | 4-8 | — | — |
| Package Size(MB) | ~100 KB | ~2.5 MB | |
| Average Latency (Hello World)(ms) | ~85 ms | — | — |
| PyPI Weekly Downloads(downloads) | ~2.8M (Jan 2026) | — | — |
| Time to Hello World API(minutes) | ~5 minutes | — | — |
| Throughput Performance(requests/second) | ~15,000 req/s | — | — |
| Memory Usage (Hello World)(MB) | ~40 MB | — | — |
| Throughput Benchmark (requests/sec)(req/s) | ~18,000 req/s | — | — |
| Framework Age(years) | 6 years (2018) | — | — |
| Stack Overflow Questions(questions) | ~30,000 questions | 40,000+ | |
| Time to Build Basic CRUD App(minutes) | 3.5 hours (manual setup required) | — | — |
| Ecosystem Size (package repositories)(packages) | ~480,000 packages (PyPI) | — | — |
| Weekly npm Downloads(downloads) | ~1.2M (PyPI: ~2.8M) | — | — |
| Cold Start Time(milliseconds) | 300ms | ~150ms | |
| Core Library Size(kilobytes) | 1,200KB (with uvicorn) | — | — |
| Requests Per Second (Throughput)(req/s) | ~22,000 req/s | ~7,500 req/s | |
| Production Deployments(organizations) | ~400K active | ~2.5M active | |
| Third-Party Extensions Available(plugins) | ~2,500 extensions | 10,000+ extensions | |
| Time to Basic Productivity(hours) | 4-8 hours | 2-4 hours | |
| Performance - Request Throughput(requests/sec) | ~15,000-18,000 req/sec | — | — |
| Request Throughput(requests/second) | ~12,000 req/s | — | — |
| Cold Start Latency(milliseconds) | 300ms | — | — |
| Weekly Package Downloads(downloads) | ~450,000 (PyPI) | — | — |
| GitHub Stars(stars) | ~80,000 stars | ~95,000 stars | |
| Production Maturity(years) | 7 years | — | — |
| P99 Latency (typical)(ms) | 150-250 | — | — |
| Peak Throughput (Req/s)(requests per second) | ~10,000 req/s | — | — |
| Memory Usage per Process(MB) | ~40 MB | — | — |
| Community Library Ecosystem(total packages) | 500,000+ PyPI packages (Python ecosystem) | — | — |
| Job Market Postings (2026)(active positions) | ~12,000 positions | — | — |
| Framework Maturity(years) | 6 years (released 2018) | — | — |
| Minimum Memory Footprint(GB) | 40MB | — | — |
| GitHub Stars (as of 2026)(stars) | 68,000+ stars | — | — |
| NPM Weekly Downloads(downloads) | 2.5M weekly | — | — |
| Time to Production Hello World(minutes) | 5 minutes | — | — |
| Built-in Features Count(features) | 12 core features | — | — |
| Production Applications (market estimate)(thousands) | 45,000+ apps | — | — |
| Throughput (Requests per Second)(req/s) | ~12,000 req/s | ~4,000 req/s | |
| Active Job Listings (2025)(positions) | 42,000 | — | — |
| Memory Usage (Idle Instance)(MB) | ~80-120 MB | — | — |
| Initial Release Year(year) | 2018 | 2010 | |
| Requests Per Second (Single Instance)(req/s) | ~7,500 req/s | — | — |
| Memory Footprint Per Process(MB) | ~15 MB | — | — |
| Time to Basic API (Hello World)(lines of code) | ~5 lines | — | — |
| Ecosystem Size (Packages)(packages) | ~350,000 PyPI packages (FastAPI-specific: ~4,000) | — | — |
| Application Startup Time(milliseconds) | 150ms (average) | — | — |
| Requests Per Second (1KB payload)(req/s) | ~28,000 | — | — |
| Available Packages/Libraries(count) | ~500,000 (PyPI) | — | — |
| NPM/PyPI Weekly Downloads(weekly downloads) | ~2.8M (PyPI/month) | — | — |
| Default Dependencies(count) | 6 (starlette, pydantic, etc.) | 1 (werkzeug) | |
| Time to 'Hello World' App(lines of code) | 8-10 lines | 4-5 lines | |
| Memory Usage (Idle)(MB) | 50-100MB | ~35 MB per instance | |
| Lines of Code for Basic Endpoint(lines) | 5-8 lines | — | — |
| GitHub Stars (2026)(stars) | ~75,000 stars | ~67,000 stars | |
| Request/Response Latency (simple GET)(ms) | 25-35 ms | 25-35 ms | |
| Weekly Downloads (PyPI)(thousands) | 850 thousand | 850 thousand | |
| Minimal Project Setup Time(minutes) | 5-10 | 5-10 | |
| Stack Overflow Questions (all-time)(count) | 1,200 thousand | 1,200 thousand | |
| Cold Start Time (Serverless)(ms) | ~450 ms | ~450 ms | |
| GitHub Stars (Community)(stars) | 68,000+ stars | 68,000+ stars | |
| Available Extensions(count (approx.)) | 2,500+ | 2,500+ | |
| Minimum Project Boilerplate(lines of code) | 5-7 lines | 5-7 lines | |
| Framework Core Size(KB) | ~150 KB | ~150 KB | |
| Average Startup Time(seconds) | ~500 ms | ~500 ms | |
| Learning Curve for Beginners(hours to proficiency) | 20-30 hours | 20-30 hours | |
| Market Share Among Web Frameworks(percent) | 70% (Python) | 70% (Python) | |
| Requests Per Second (Concurrent Load)(RPS) | ~2,500 RPS | ~2,500 RPS | |
| Requests Per Second (Benchmark)(req/s) | ~1,200 req/s | ~1,200 req/s | |
| Memory Usage (Single Instance)(MB) | 75 MB | 75 MB | |
| Time to 'Hello World'(minutes) | 3 minutes | 3 minutes | |
| Available Extensions/Packages(count) | 15,000+ packages | 15,000+ packages | |
| Recommended Learning Duration(weeks) | 2-3 weeks | 2-3 weeks | |
| Job Postings (Global, 2025)(jobs) | 23,500 positions | 23,500 positions | |
| Production Deployments (Est.)(years in market) | 12+ years | 12+ years | |
| Ecosystem Extensions(packages) | 5,000+ | 5,000+ | |
| Time to Build First App(hours) | ~2 hours | ~2 hours | |
| Concurrent Connection Limit (Practical)(connections) | 500 optimal | 500 optimal | |
| Active Contributors(developers) | 2,500+ | 2,500+ | |
| Available Packages/Gems(count) | 500,000+ | 500,000+ | |
| Global Job Openings (2024)(positions) | 45,000+ | 45,000+ | |
| Minimum Code Boilerplate (Hello World)(lines) | 12 lines | 12 lines | |
| Setup Time to First Running App(minutes) | 8-12 minutes | 8-12 minutes | |
| Average Community Response Time (GitHub Issues)(hours) | 24-36 hours | 24-36 hours | |
| Third-Party Extensions(extensions) | 800+ | 800+ | |
| Production Deployments (Estimated)(count) | 2.5M+ | 2.5M+ | |
| Memory Usage (Baseline)(MB) | ~30MB | ~30MB | |
| Available Packages/Modules(count) | ~150,000+ PyPI packages | ~150,000+ PyPI packages | |
| GitHub Stars (Popularity Proxy)(stars) | ~67,000 stars | ~67,000 stars | |
| Time to First Hello World(lines of code) | 4 lines | 4 lines |
Sourced from publicly available data ·
Key Differences
7 attributes compared head-to-head
F
5FastAPIFastAPI leads
F
2FlaskFastAPI
Attribute
Flask
- ~12,000 req/s(winner)Request Performance (requests/sec)~4,000 req/s
- Native, built-in by default(winner)Async/Await SupportLimited, requires external libraries
- OpenAPI/Swagger auto-generated(winner)Automatic API DocumentationManual setup required
- 15-25 hoursLearning Curve (hours to productivity)5-10 hours(winner)
- 4 years (2021)Ecosystem Maturity (years since release)18 years (2010)(winner)
- Pydantic models, automatic validation(winner)Built-in Data ValidationNone, requires add-ons
- ~75,000 stars(winner)GitHub Stars (as of 2026)~67,000 stars
- Request Performance (requests/sec)
FastAPI
~12,000 req/s(winner)
Flask
~4,000 req/s
- Async/Await Support
FastAPI
Native, built-in by default(winner)
Flask
Limited, requires external libraries
- Automatic API Documentation
FastAPI
OpenAPI/Swagger auto-generated(winner)
Flask
Manual setup required
- Learning Curve (hours to productivity)
FastAPI
15-25 hours
Flask
5-10 hours(winner)
- Ecosystem Maturity (years since release)
FastAPI
4 years (2021)
Flask
18 years (2010)(winner)
- Built-in Data Validation
FastAPI
Pydantic models, automatic validation(winner)
Flask
None, requires add-ons
- GitHub Stars (as of 2026)
FastAPI
~75,000 stars(winner)
Flask
~67,000 stars
Full Comparison
| Attribute | FastAPI | Flask |
|---|---|---|
| Async/Await Native Support | Yes, built-in by default | No, requires external libraries |
| Built-in Admin Dashboard | No, requires build | — |
| Async Request Support | Full native support | — |
| Auto API Documentation | Native (Swagger UI + ReDoc built-in) | — |
| Native Async/Await Support | Native first-class support | Experimental in Flask 2.0+ |
Show 13 more attributesBuilt-in ORM No (requires external library) — Auto-generated API Documentation Yes (automatic) — Built-in Data Validation Yes, Pydantic models with automatic validation No, requires add-ons Built-in API Documentation Yes (Swagger UI + ReDoc automatic) — Native Type Validation Yes (Pydantic built-in) — Built-in Authentication No (requires FastAPI-Users, python-jose) — Database ORM Included No (requires SQLAlchemy, Tortoise-ORM) — Auto-Generated API Docs Yes (Swagger/ReDoc) — Built-in Database ORM(feature) None (use SQLAlchemy separately) — Admin Interface Requires manual or third-party setup — WebSocket Support No (requires Flask-SocketIO) — Data Science Library Integration Native (NumPy, TensorFlow, Pandas) — Built-in ORM Support Via SQLAlchemy extension — | ||
| Automatic API Documentation | Yes, OpenAPI/Swagger auto-generated | No, manual setup required |
| Type Safety Support | Native (Python type hints) | — |
| Auto-Documentation Support | Built-in (OpenAPI 3.0) | Manual integration required |
| Built-in Documentation Generation | Automatic (Swagger UI + ReDoc) | — |
| Built-in Request Validation | Yes (Pydantic) | — |
Show 8 more attributesTime to Hello World API(minutes) ~5 minutes — Built-in Validation Framework Pydantic (integrated) — Built-in Features Count(features) 12 core features — Type Hint Support Full (enforced) Optional Auto Documentation Generation Automatic (Swagger UI + ReDoc) Manual (requires Flask-RESTX, Flasgger) Time to 'Hello World' App(lines of code) 8-10 lines 4-5 lines Time to 'Hello World'(minutes) 3 minutes — Recommended Learning Duration(weeks) 2-3 weeks — | ||
| Time to First API (Learning Curve)(hours) | 15-25 hours | 5-10 hours(winner) |
| Learning Curve Difficulty | Moderate (3.5/5) | Easy (1.5/5)(winner) |
| Core Framework Size(KB) | ~300 KB | ~60 KB(winner) |
| Time Since Initial Release(years) | 4 years (2021) | 18 years (2010)(winner) |
| Framework Age(years) | 6 years (2018) | — |
| Production Deployments (Est.)(years in market) | 12+ years | — |
| Throughput (Requests/Second)(req/s) | 8,000-12,000(winner) | 400-600 |
| Startup Time(milliseconds) | 250-500ms | ~150ms(winner) |
| Memory Usage (base)(MB) | ~10MB | — |
| Latency (p99 response time)(ms) | 8-12 ms | — |
| Framework Requests Per Second(req/s) | 10,000 | — |
Show 23 more attributesAverage Latency (Hello World)(ms) ~85 ms — Throughput Performance(requests/second) ~15,000 req/s — Memory Usage (Hello World)(MB) ~40 MB — Throughput Benchmark (requests/sec)(req/s) ~18,000 req/s — Cold Start Time(milliseconds) 300ms ~150ms Requests Per Second (Throughput)(req/s) ~22,000 req/s ~7,500 req/s Performance - Request Throughput(requests/sec) ~15,000-18,000 req/sec — Request Throughput(requests/second) ~12,000 req/s — Cold Start Latency(milliseconds) 300ms — P99 Latency (typical)(ms) 150-250 — Peak Throughput (Req/s)(requests per second) ~10,000 req/s — Throughput (Requests per Second)(req/s) ~12,000 req/s ~4,000 req/s Memory Usage (Idle Instance)(MB) ~80-120 MB — Requests Per Second (Single Instance)(req/s) ~7,500 req/s — Memory Footprint Per Process(MB) ~15 MB — Application Startup Time(milliseconds) 150ms (average) — Requests Per Second (1KB payload)(req/s) ~28,000 — Request/Response Latency (simple GET)(ms) 25-35 ms — Framework Core Size(KB) ~150 KB — Average Startup Time(seconds) ~500 ms — Requests Per Second (Concurrent Load)(RPS) ~2,500 RPS — Requests Per Second (Benchmark)(req/s) ~1,200 req/s — Memory Usage (Baseline)(MB) ~30MB — | ||
| Time to First API Endpoint(minutes) | ~5 minutes(winner) | 7 minutes |
| Time to Production (Small API)(hours) | 4-8 | — |
| Time to Production Hello World(minutes) | 5 minutes | — |
| Time to Basic API (Hello World)(lines of code) | ~5 lines | — |
| Third-party Packages(packages) | 2,000+ packages | — |
| Package Ecosystem Size(packages) | 500,000+ (PyPI)(winner) | 300,000+ (PyPI) |
| Related Packages (PyPI)(packages) | ~2,100 | ~8,500(winner) |
| Python/Go Package Ecosystem Size(packages) | 400,000+ | — |
| Ecosystem Size (package repositories)(packages) | ~480,000 packages (PyPI) | — |
Show 11 more attributesWeekly Package Downloads(downloads) ~450,000 (PyPI) — Community Library Ecosystem(total packages) 500,000+ PyPI packages (Python ecosystem) — Ecosystem Size (Packages)(packages) ~350,000 PyPI packages (FastAPI-specific: ~4,000) — Available Packages/Libraries(count) ~500,000 (PyPI) — Available Extensions(count (approx.)) 2,500+ — Available Extensions/Packages(count) 15,000+ packages — Ecosystem Extensions(packages) 5,000+ — Available Packages/Gems(count) 500,000+ — Third-Party Extensions(extensions) 800+ — Available Packages/Modules(count) ~150,000+ PyPI packages — ML/Data Science Library Support(text) Native: NumPy, Pandas, Scikit-learn, TensorFlow, PyTorch — | ||
| Production Adoption Rate(percent) | 22% (Stack Overflow 2024) | — |
| First Release Year | 2018 | — |
| Initial Release Year(year) | 2018 | 2010(winner) |
| Minimum Python Version(version) | Python 3.6+ | Python 2.7+ (legacy) / 3.4+ |
| Minimum Python/Node Version | Python 3.7+ | — |
| Idle Memory Usage(MB) | 50-80 | — |
| Memory Usage (Idle)(MB) | 50-100MB | ~35 MB per instance(winner) |
| Deployment Model | Requires app server (Uvicorn) | — |
| Native Async Support | Native (async/await throughout) | — |
| Built-in Dependency Injection(feature availability) | Manual setup required | — |
| Async Support Quality | Native async/await with asyncio | — |
| Framework Type | High-level API framework (built on Starlette) | — |
Show 2 more attributesAsync Support Native async/await built-in Requires Flask-APScheduler or manual async setup Concurrency Model Synchronous (WSGI) — | ||
| Package Size(MB) | ~100 KB | ~2.5 MB(winner) |
| Default Dependencies(count) | 6 (starlette, pydantic, etc.) | 1 (werkzeug)(winner) |
| PyPI Weekly Downloads(downloads) | ~2.8M (Jan 2026) | — |
| Production Deployments(organizations) | ~400K active | ~2.5M active(winner) |
| Production Applications (market estimate)(thousands) | 45,000+ apps | — |
| NPM/PyPI Weekly Downloads(weekly downloads) | ~2.8M (PyPI/month) | — |
| Market Share Among Web Frameworks(percent) | 70% (Python) | — |
Show 1 more attributeProduction Deployments (Estimated)(count) 2.5M+ — | ||
| Python Version Support(versions) | 3.7+ | — |
| Stack Overflow Questions(questions) | ~30,000 questions | 40,000+(winner) |
| Weekly npm Downloads(downloads) | ~1.2M (PyPI: ~2.8M) | — |
| GitHub Stars (2026)(stars) | ~75,000 stars(winner) | ~67,000 stars |
| Stack Overflow Questions (all-time)(count) | 1,200 thousand | — |
| GitHub Stars (Community)(stars) | 68,000+ stars | — |
Show 2 more attributesActive Contributors(developers) 2,500+ — GitHub Stars (Popularity Proxy)(stars) ~67,000 stars — | ||
| Time to Build Basic CRUD App(minutes) | 3.5 hours (manual setup required) | — |
| Lines of Code for Basic Endpoint(lines) | 5-8 lines | — |
| Minimal Project Setup Time(minutes) | 5-10 | — |
| Minimum Code Boilerplate (Hello World)(lines) | 12 lines | — |
| Setup Time to First Running App(minutes) | 8-12 minutes | — |
| Async-First Support | Native, default behavior | — |
| Core Library Size(kilobytes) | 1,200KB (with uvicorn) | — |
| Third-Party Extensions Available(plugins) | ~2,500 extensions | 10,000+ extensions(winner) |
| Time to Basic Productivity(hours) | 4-8 hours | 2-4 hours(winner) |
| GitHub Stars(stars) | ~80,000 stars | ~95,000 stars(winner) |
| NPM Weekly Downloads(downloads) | 2.5M weekly | — |
| Weekly Downloads (PyPI)(thousands) | 850 thousand | — |
| Production Maturity(years) | 7 years | — |
| Memory Usage per Process(MB) | ~40 MB | — |
| Minimum Memory Footprint(GB) | 40MB | — |
| Memory Usage (Single Instance)(MB) | 75 MB | — |
| Job Market Postings (2026)(active positions) | ~12,000 positions | — |
| Framework Maturity(years) | 6 years (released 2018) | — |
| GitHub Stars (as of 2026)(stars) | 68,000+ stars | — |
| Active Job Listings (2025)(positions) | 42,000 | — |
| Learning Curve(hours) | 30-40 hours | — |
| Time to First Hello World(lines of code) | 4 lines | — |
| Production Readiness Without External Server | Requires ASGI (Uvicorn) | — |
| Authentication Built-in | No (use Flask-Login or similar) | — |
| Cold Start Time (Serverless)(ms) | ~450 ms | — |
| Concurrent Connection Limit (Practical)(connections) | 500 optimal | — |
| Minimum Project Boilerplate(lines of code) | 5-7 lines | — |
| Learning Curve for Beginners(hours to proficiency) | 20-30 hours | — |
| Job Postings (Global, 2025)(jobs) | 23,500 positions | — |
| Time to Build First App(hours) | ~2 hours | — |
| Global Job Openings (2024)(positions) | 45,000+ | — |
| Built-in Request/Response Handling | Yes (Werkzeug-based) | — |
| Average Community Response Time (GitHub Issues)(hours) | 24-36 hours | — |
| Deployment Without Extra Server(text) | No - requires WSGI server (Gunicorn, uWSGI) | — |
FFastAPI
FFlask
Async/Await Native Support
Yes, built-in by default
No, requires external libraries
Built-in Admin Dashboard
No, requires build
—
Async Request Support
Full native support
—
Auto API Documentation
Native (Swagger UI + ReDoc built-in)
—
Native Async/Await Support
Native first-class support
Experimental in Flask 2.0+
Show 13 more attributes
Built-in ORM
No (requires external library)
—
Auto-generated API Documentation
Yes (automatic)
—
Built-in Data Validation
Yes, Pydantic models with automatic validation
No, requires add-ons
Built-in API Documentation
Yes (Swagger UI + ReDoc automatic)
—
Native Type Validation
Yes (Pydantic built-in)
—
Built-in Authentication
No (requires FastAPI-Users, python-jose)
—
Database ORM Included
No (requires SQLAlchemy, Tortoise-ORM)
—
Auto-Generated API Docs
Yes (Swagger/ReDoc)
—
Built-in Database ORM(feature)
None (use SQLAlchemy separately)
—
Admin Interface
Requires manual or third-party setup
—
WebSocket Support
No (requires Flask-SocketIO)
—
Data Science Library Integration
Native (NumPy, TensorFlow, Pandas)
—
Built-in ORM Support
Via SQLAlchemy extension
—
Automatic API Documentation
Yes, OpenAPI/Swagger auto-generated
No, manual setup required
Type Safety Support
Native (Python type hints)
—
Auto-Documentation Support
Built-in (OpenAPI 3.0)
Manual integration required
Built-in Documentation Generation
Automatic (Swagger UI + ReDoc)
—
Built-in Request Validation
Yes (Pydantic)
—
Show 8 more attributes
Time to Hello World API(minutes)
~5 minutes
—
Built-in Validation Framework
Pydantic (integrated)
—
Built-in Features Count(features)
12 core features
—
Type Hint Support
Full (enforced)
Optional
Auto Documentation Generation
Automatic (Swagger UI + ReDoc)
Manual (requires Flask-RESTX, Flasgger)
Time to 'Hello World' App(lines of code)
8-10 lines
4-5 lines
Time to 'Hello World'(minutes)
3 minutes
—
Recommended Learning Duration(weeks)
2-3 weeks
—
Time to First API (Learning Curve)(hours)
15-25 hours
5-10 hours
Learning Curve Difficulty
Moderate (3.5/5)
Easy (1.5/5)
Core Framework Size(KB)
~300 KB
~60 KB
Time Since Initial Release(years)
4 years (2021)
18 years (2010)
Framework Age(years)
6 years (2018)
—
Production Deployments (Est.)(years in market)
12+ years
—
Throughput (Requests/Second)(req/s)
8,000-12,000
400-600
Startup Time(milliseconds)
250-500ms
~150ms
Memory Usage (base)(MB)
~10MB
—
Latency (p99 response time)(ms)
8-12 ms
—
Framework Requests Per Second(req/s)
10,000
—
Show 23 more attributes
Average Latency (Hello World)(ms)
~85 ms
—
Throughput Performance(requests/second)
~15,000 req/s
—
Memory Usage (Hello World)(MB)
~40 MB
—
Throughput Benchmark (requests/sec)(req/s)
~18,000 req/s
—
Cold Start Time(milliseconds)
300ms
~150ms
Requests Per Second (Throughput)(req/s)
~22,000 req/s
~7,500 req/s
Performance - Request Throughput(requests/sec)
~15,000-18,000 req/sec
—
Request Throughput(requests/second)
~12,000 req/s
—
Cold Start Latency(milliseconds)
300ms
—
P99 Latency (typical)(ms)
150-250
—
Peak Throughput (Req/s)(requests per second)
~10,000 req/s
—
Throughput (Requests per Second)(req/s)
~12,000 req/s
~4,000 req/s
Memory Usage (Idle Instance)(MB)
~80-120 MB
—
Requests Per Second (Single Instance)(req/s)
~7,500 req/s
—
Memory Footprint Per Process(MB)
~15 MB
—
Application Startup Time(milliseconds)
150ms (average)
—
Requests Per Second (1KB payload)(req/s)
~28,000
—
Request/Response Latency (simple GET)(ms)
25-35 ms
—
Framework Core Size(KB)
~150 KB
—
Average Startup Time(seconds)
~500 ms
—
Requests Per Second (Concurrent Load)(RPS)
~2,500 RPS
—
Requests Per Second (Benchmark)(req/s)
~1,200 req/s
—
Memory Usage (Baseline)(MB)
~30MB
—
Time to First API Endpoint(minutes)
~5 minutes
7 minutes
Time to Production (Small API)(hours)
4-8
—
Time to Production Hello World(minutes)
5 minutes
—
Time to Basic API (Hello World)(lines of code)
~5 lines
—
Third-party Packages(packages)
2,000+ packages
—
Package Ecosystem Size(packages)
500,000+ (PyPI)
300,000+ (PyPI)
Related Packages (PyPI)(packages)
~2,100
~8,500
Python/Go Package Ecosystem Size(packages)
400,000+
—
Ecosystem Size (package repositories)(packages)
~480,000 packages (PyPI)
—
Show 11 more attributes
Weekly Package Downloads(downloads)
~450,000 (PyPI)
—
Community Library Ecosystem(total packages)
500,000+ PyPI packages (Python ecosystem)
—
Ecosystem Size (Packages)(packages)
~350,000 PyPI packages (FastAPI-specific: ~4,000)
—
Available Packages/Libraries(count)
~500,000 (PyPI)
—
Available Extensions(count (approx.))
2,500+
—
Available Extensions/Packages(count)
15,000+ packages
—
Ecosystem Extensions(packages)
5,000+
—
Available Packages/Gems(count)
500,000+
—
Third-Party Extensions(extensions)
800+
—
Available Packages/Modules(count)
~150,000+ PyPI packages
—
ML/Data Science Library Support(text)
Native: NumPy, Pandas, Scikit-learn, TensorFlow, PyTorch
—
Production Adoption Rate(percent)
22% (Stack Overflow 2024)
—
First Release Year
2018
—
Initial Release Year(year)
2018
2010
Minimum Python Version(version)
Python 3.6+
Python 2.7+ (legacy) / 3.4+
Minimum Python/Node Version
Python 3.7+
—
Idle Memory Usage(MB)
50-80
—
Memory Usage (Idle)(MB)
50-100MB
~35 MB per instance
Deployment Model
Requires app server (Uvicorn)
—
Native Async Support
Native (async/await throughout)
—
Built-in Dependency Injection(feature availability)
Manual setup required
—
Async Support Quality
Native async/await with asyncio
—
Framework Type
High-level API framework (built on Starlette)
—
Show 2 more attributes
Async Support
Native async/await built-in
Requires Flask-APScheduler or manual async setup
Concurrency Model
Synchronous (WSGI)
—
Package Size(MB)
~100 KB
~2.5 MB
Default Dependencies(count)
6 (starlette, pydantic, etc.)
1 (werkzeug)
PyPI Weekly Downloads(downloads)
~2.8M (Jan 2026)
—
Production Deployments(organizations)
~400K active
~2.5M active
Production Applications (market estimate)(thousands)
45,000+ apps
—
NPM/PyPI Weekly Downloads(weekly downloads)
~2.8M (PyPI/month)
—
Market Share Among Web Frameworks(percent)
70% (Python)
—
Show 1 more attribute
Production Deployments (Estimated)(count)
2.5M+
—
Python Version Support(versions)
3.7+
—
Stack Overflow Questions(questions)
~30,000 questions
40,000+
Weekly npm Downloads(downloads)
~1.2M (PyPI: ~2.8M)
—
GitHub Stars (2026)(stars)
~75,000 stars
~67,000 stars
Stack Overflow Questions (all-time)(count)
1,200 thousand
—
GitHub Stars (Community)(stars)
68,000+ stars
—
Show 2 more attributes
Active Contributors(developers)
2,500+
—
GitHub Stars (Popularity Proxy)(stars)
~67,000 stars
—
Time to Build Basic CRUD App(minutes)
3.5 hours (manual setup required)
—
Lines of Code for Basic Endpoint(lines)
5-8 lines
—
Minimal Project Setup Time(minutes)
5-10
—
Minimum Code Boilerplate (Hello World)(lines)
12 lines
—
Setup Time to First Running App(minutes)
8-12 minutes
—
Async-First Support
Native, default behavior
—
Core Library Size(kilobytes)
1,200KB (with uvicorn)
—
Third-Party Extensions Available(plugins)
~2,500 extensions
10,000+ extensions
Time to Basic Productivity(hours)
4-8 hours
2-4 hours
GitHub Stars(stars)
~80,000 stars
~95,000 stars
NPM Weekly Downloads(downloads)
2.5M weekly
—
Weekly Downloads (PyPI)(thousands)
850 thousand
—
Production Maturity(years)
7 years
—
Memory Usage per Process(MB)
~40 MB
—
Minimum Memory Footprint(GB)
40MB
—
Memory Usage (Single Instance)(MB)
75 MB
—
Job Market Postings (2026)(active positions)
~12,000 positions
—
Framework Maturity(years)
6 years (released 2018)
—
GitHub Stars (as of 2026)(stars)
68,000+ stars
—
Active Job Listings (2025)(positions)
42,000
—
Learning Curve(hours)
30-40 hours
—
Time to First Hello World(lines of code)
4 lines
—
Production Readiness Without External Server
Requires ASGI (Uvicorn)
—
Authentication Built-in
No (use Flask-Login or similar)
—
Cold Start Time (Serverless)(ms)
~450 ms
—
Concurrent Connection Limit (Practical)(connections)
500 optimal
—
Minimum Project Boilerplate(lines of code)
5-7 lines
—
Learning Curve for Beginners(hours to proficiency)
20-30 hours
—
Job Postings (Global, 2025)(jobs)
23,500 positions
—
Time to Build First App(hours)
~2 hours
—
Global Job Openings (2024)(positions)
45,000+
—
Built-in Request/Response Handling
Yes (Werkzeug-based)
—
Average Community Response Time (GitHub Issues)(hours)
24-36 hours
—
Deployment Without Extra Server(text)
No - requires WSGI server (Gunicorn, uWSGI)
—
Pros & Cons
10 pros·4 cons across both
F
F
F
FastAPI
+5-2
Pros
- 3x faster throughput (~12,000 req/s vs 4,000 req/s) due to async/Starlette foundation
- Automatic OpenAPI/Swagger documentation generation with zero configuration
- Built-in Pydantic data validation, serialization, and type hints with IDE support
- Native async/await support for concurrent request handling and background tasks
- Request/response validation with automatic error responses (422 Unprocessable Entity)
Cons
- Steeper learning curve for developers unfamiliar with async Python concepts
- Smaller ecosystem and fewer third-party extensions compared to Flask's 18-year maturity
F
Flask
+5-2
Pros
- Minimal learning curve (5-10 hours to productivity) with straightforward, readable code
- Highly flexible architecture—no imposed conventions, full control over project structure
- Massive ecosystem with 18 years of community contributions and third-party packages
- Lightweight core (~60KB) with optional extensions for features like ORM, forms, or caching
- Excellent for prototyping and small-to-medium projects due to low configuration overhead
Cons
- Synchronous by default, requiring manual async implementation with external libraries
- No built-in API documentation—must manually create OpenAPI specs or use Flasgger/Connexion
Frequently Asked Questions
5 questions
FastAPI is approximately 3x faster than Flask. Benchmark testing shows FastAPI handles ~12,000 requests/second while Flask handles ~4,000 requests/second on comparable hardware. This performance advantage comes from FastAPI's async-first design built on Starlette, whereas Flask handles requests synchronously by default. For most small projects, this difference is negligible, but for high-traffic APIs or real-time systems, FastAPI's throughput advantage is significant.
Resources & Learn More
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