Uvicorn vs flask. There’s also Quart that uses Hypercorn instead of .
Uvicorn vs flask. ASGI ¶ If you’d like to use an ASGI server you will need to utilise WSGI to ASGI middleware. Generally Flask on a Greenlet powered WSGI server (Meinheld / Gevent) can offer comparable throughput as an async-first ASGI framework like FastAPI. Click to make an informed choice! Oct 26, 2022 · The application I deploy is FastAPI with Uvicorn under K8s. However, there are some key differences between the two frameworks. uvicorn listens on a socket, receives the connection, does a bit processing and hands the request over to FastAPI, according to the ASGI interface. In the last few years, though, there have been many new Jul 7, 2024 · One of the most significant differences between FastAPI and Flask is their performance characteristics. g Uvicorn), starting a single process, listening on all the IPs (0. This is the basic idea. Uvicorn is an ASGI web server implementation for Python. Jul 7, 2023 · Photo by Fotis Fotopoulos on Unsplash In this tutorial, we will explore how to build a simple web application using Starlette, a lightweight asynchronous web framework, and Uvicorn, a lightning-fast ASGI server. It's like traditional HTML, meets stronger typing, meets niche Jun 16, 2021 · However, Flask is fundamentally constrained in that it is a WSGI application. Configuration Methods There are three ways to configure Uvicorn: Command Line: Use command line options when running Uvicorn directly. Compare Django, Flask, and FastAPI – their strengths, trade-offs, and key differences. By default, Gunicorn workers are synchronous, which handle a single request at a time. May 29, 2021 · And now I am thinking about deploying it however I seem to get strange unexpected performance issues that seem to depend on wether I use uvicorn vs gunicorn. Jul 7, 2024 · One of the most significant differences between FastAPI and Flask is their performance characteristics. Jul 13, 2023 · Understanding the fundamental concepts of multithreading, multiprocessing, and AsyncIO is pivotal to harnessing the full potential of Flask with Gunicorn and FastAPI with Uvicorn. Uvicorn is the default Asynchronous Server Gateway Sep 16, 2020 · As per documentation, FastAPI is built on top of Starlette which itself is built on top of Uvicorn. And this is a matter of routing data in and out of some external tool, similar to the way Flask does with Gunicorn (or more commonly today, Uvicorn). I would, however, say that as things get If you don’t like docker you could try uwsgi on cygwin for windows. Nov 15, 2024 · 本文针对那些有兴趣从Flask转移到FastAPI的人，比较和对比了Flask和FastAPI的常见模式。#FastAPIvsFlask@app. Learn ASGI vs WSGI differences, use cases, and performance benchmarks. See the uvicorn documentation for more details or check this overview of available ASGI servers for other options. NET API. FastAPI on the other hand implements the ASGI specification. The following instructions describe how to set the appropriate application port and root path for an app run with the Uvicorn ASGI server. Jul 19, 2020 · I have been tinkering around Flask and FastAPI to see how it acts as a server. Additionally run behind Nginx for self-hosted deployments. If you already have Flask apps, it is much easier to turn them into Quart apps than FastAPI apps, given the purposeful similarity of Quart to The numbers only serve to indicate the relative performance of these frameworks under the specific testing conditions. Sep 8, 2022 · Compare Flask vs FastAPI for Python web apps—simplicity and flexibility vs high-performance async, auto-validation, and API docs. The way it works is that it creates and maintains their operability a configurable number of application instances (aka workers) that serve requests from clients. But when checking benchmarks and comparisons you should keep the following in mind. 0) on a predefined port (e. Python 3. It is designed to run asynchronous Python web applications, particularly those built with frameworks like FastAPI, Starlette, and others. Discover here which one you should choose for your project. Opt for Uvicorn If… You’re building a modern, async web application that benefits from real-time features. Jun 11, 2021 · Problem description I am trying to create a Flask app that should: Be visible on localhost only, so no network slowdown Get quite a lot of data (30MB as a large numpy array) as input and output a Dec 12, 2023 · Explore the benefits and features of FastAPI and Flask to make the right selection for your app development needs. Mar 24, 2021 · Scale your wsgi project to the next level by leveraging everything Gunicorn has to offer. Whether you're Jan 10, 2025 · What is Uvicorn? Answer: Uvicorn is a very fast ASGI (Asynchronous Server Gateway Tagged with fastapi, python, django, flask. Sep 22, 2025 · An overview of how to create and deploy a containerized Python web app (Flask or FastAPI) on Azure App Service. If you have been dabbling in this area, you'd have probably used some of the most popular web frameworks already — Django, Flask, Falcon, Tornado, CherryPy, among others. Benchmark scripts to send a configurable number of concurrent requests. Uvicorn is an ASGI web server implementation for Python. WebSocket Applications: For applications requiring real-time features, Quart's native WebSocket support is beneficial. As a general rule, you probably want to: Run uvicorn --reload from the command line for local development. Compare build-a-saas-app-with-flask vs uvicorn and see what are their differences. Contribute to emmett-framework/granian development by creating an account on GitHub. GitHub Gist: instantly share code, notes, and snippets. Feb 1, 2024 · Choosing between Python FastAPI vs Flask? FastAPI is for high-performance APIs, while Flask is for small to medium web apps and APIs. The simpler the problem solved by the tool, the better performance it will get. middleware("http")装饰器是在FastAPI中… Jan 1, 2022 · Flask with the “flask run” server had a large number of non-2xx or 3xx responses, as expected of a development server. 9 or higher installed locally. Just flip a coin if you have to. Jul 30, 2024 · When to Use Quart Existing Flask Applications: If you have a Flask app and want to add asynchronous features, Quart is an excellent choice. Finally, run everything behind a CDN for caching Python 是一种功能强大的编程语言，广泛应用于 Web 开发领域。 FastAPI 和 Flask 是 Python Web 开发中最受欢迎的两个轻量框架（相比于 Django）。本文将对 FastAPI 和 Flask 进行综合对比，探讨它们在语法和表达能力、生态系统和社区支持、性能和扩展性、开发工具和调试支持、安全性和稳定性、学习曲线和 Oct 15, 2023 · Order Up! FastAPI vs Flask in the Kitchen of RESTful APIs Introduction Building RESTful API applications is an essential part of many software projects, especially when data needs to be shared or … May 27, 2025 · When deploying FastAPI applications in production, developers often face confusion about whether to use Gunicorn, Uvicorn, or both. Concurrency Model: Gunicorn follows a pre-fork worker model, where a master process forks multiple worker processes to handle incoming requests. Flask vs Gunicorn: What are the differences? Flask vs Gunicorn Flask and Gunicorn are both popular frameworks used in web development, but they have key differences in terms of their functionality and performance. Python never runs more than 1 thread per process because of the GIL. FastAPI: Modern and High-Performance Overview Feb 23, 2024 · Similar to Gunicorn, Waitress is a lightweight pure-Python WSGI server designed to be fast, efficient, and easy to use, making it suitable for deploying small to medium-sized web applications Jun 30, 2023 · This means that Gunicorn can serve applications written in frameworks such as Flask or Django (more so for versions released before 2021). However, Gunicorn also supports asynchronous workers Jul 4, 2024 · Today, we’ll compare three popular ASGI servers — Uvicorn, Hypercorn, and Daphne — using a simple application to compare their performance. Benchmarks and speed When you check the benchmarks, it is common to see several Oct 27, 2020 · For the application components, a small microservice that performs a database query and returns the result as a JSON response is used. Machine Specs: Mar 24, 2024 · In the wild web jungle, where websites roam free, two server creatures battle for dominance: Gunicorn, the majestic green unicorn, and Uvicorn, its sleek, sparkly cousin! One thrives in a calm savanna, the other in a neon-lit dance club. Sep 17, 2024 · pythonでFlaskやFastAPIで開発する際に外部サーバーとして使用する 「Gunicorn」と「Uvicorn」についてそれぞれの特徴と違いを調べたのでまとめておく。 Deployment Server deployment is a complex area, that will depend on what kind of service you're deploying Uvicorn onto. Here are the key differences between the two. Quickstart Uvicorn is available on PyPI Oct 13, 2024 · Stop using Flask and leverage FastAPI along with Uvicorn to create a superfast PDF Parsing REST service in less than 15 mins. Jun 4, 2025 · In this quickstart, you deploy a Python web app (Django, Flask, or FastAPI) to Azure App Service. FastAPI About Benchmarks Independent TechEmpower benchmarks show FastAPI applications running under Uvicorn as one of the fastest Python frameworks available, only below Starlette and Uvicorn themselves (used internally by FastAPI). Uvicorn supports HTTP/1. So I get that we’re dealing with Flask-like decorators. x) you can get a performance boost by making use of an event loop within path operations, your Flask server will still tie up a worker for each request. You can use the adapter by wrapping the Flask app, May 29, 2025 · FastAPI with Uvicorn outperforms Flask and Django in throughput benchmarks. For example, it doesn't provide tools for routing by paths. Apr 21, 2025 · This repository contains a performance comparison between a traditional Flask application, an async Quart application, a FastAPI application, and a Django application, all using Gunicorn with Uvicorn workers. Commonly paired with frameworks like Flask and Django, Gunicorn boasts a mature ecosystem and is favored for production deployments. Scripts to orchestrate the server startup, benchmark execution, and Gunicorn vs Waitress: What are the differences? Gunicorn and Waitress are both Python web servers used for deploying web applications. This can lead to slower performance under high load or when dealing with I/O-bound operations. This will help analyze the FastAPI vs Flask performance benchmark so you know which works best for you. One of the main things that I would like to know is how Flask and FastAPI deal with multiple requests from multiple clients. On the other hand, Uvicorn is an ASGI framework which has been developed with asynchronous in mind and can interact directly with the underlying Fastapi application. Mar 28, 2022 · This article, which is aimed for those interested in moving from Flask to FastAPI, compares and contrasts common patterns in both Flask and FastAPI. Jan 16, 2022 · Discover a comparison of Flask, Quart, and FastAPI focusing on Pydantic-based validation, OpenAPI schema generation, and related frameworks like Flask-Pydantic-Spec and Starlette. workers. If you are at the level where you are asking this question, then it doesn't matter. g. Feb 18, 2025 · Read this blog to find the best Python web framework for your project. It is not a web framework, but a server. route("/test") def test(): a, b Flask VS uvicorn Compare Flask vs uvicorn and see what are their differences. If your app gets big enough to the point where the differences actually matter, you'll have money, a team of engineers, and the resources to switch (if necessary). Quickstart Install Python frameworks benchmarksRead about the benchmark: The Methodic Check complete results for the latest benchmark here: Results (2022-03-14) Combined results This includes uvicorn[standard], which includes some dependencies (e. UvicornWorker) in order to communicate with the asynchronous calls. Dec 2, 2024 · When building FastAPI applications, you’re bound to encounter names like Uvicorn, Gunicorn, and even Daphne. fastapi-cli[standard] - to provide the fastapi command. Jul 23, 2025 · Flask and FastAPI are both Python web frameworks that can be used to build web applications and APIs. To complete this quickstart, you need: An Azure account with an active subscription. So the suggestion would be to use Uvicorn since it is used by FastAPI under the hood. Specifically, to see Uvicorn, Starlette and FastAPI compared together (among many other tools). An ASGI app First, let's make a simple ASGI app, and save it in the current directory with the filename simpleasgi. May 5, 2023 · はじめに 今回の記事では、PythonでWeb開発を進める際に使われるWebフレームワークである「FastAPI」と「Flask」について、両者それぞれの特徴と強みを具体的なソースコードを用いて解説する。 この記事の対象とする読者 これからPythonでWeb開発を進めることを検討している人 APIを開発したいもの Uvicorn is an ASGI web server implementation for Python. It's (simplified) the binding element that handles the web connections from the browser or api client and then allows FastAPI to serve the actual request. Jun 29, 2020 · While Flask has become the de-facto choice for API development in Machine Learning projects, there is a new framework called FastAPI that has been getting a lot of community traction. Even if you Nov 12, 2019 · Python has been the go to language for building web services, right from quick-and-dirty RESTful APIs to full-fledged web applications that serve millions of users. There’s also Quart that uses Hypercorn instead of Jun 28, 2022 · Python's AsyncIO web ecosystem continues to mature, but should you build your next production application with one of these shiny new frameworks such as FastAPI, Starlette, or Quart? Uvicorn Uvicorn is a lightning-fast ASGI server, built on uvloop and httptools. It is the recommended server for Starlette and FastAPI. Apr 29, 2023 · This means that Gunicorn will have to use some layer of abstraction (uvicorn. Simplified Migration: Developers comfortable with Flask will find Quart's API familiar. Let’s untangle their tales and see which server is the perfect fit for your web adventure! IMO, Flask is easier than fastAPI. Run gunicorn -k uvicorn. However, Python’s advent into this domain is arguably one of the most significant landmarks. Jul 27, 2020 · Three prominent ASGI servers are all good options for testing and running your ASGI app: Uvicorn, Hypercorn, and Daphne. The async architecture processes multiple prediction requests simultaneously without blocking. While Python was conceived in the late 1980s as a general-purpose programming language, it Nov 18, 2024 · A comprehensive guide to Simplifying Legacy Code with Flask and ASGI. FastAPI, as I have used them for a number of AI-on-Azure samples. middleware("http")装饰器是在FastAPI中… Jun 26, 2024 · Simplicity is key, and you’re using frameworks like Django or Flask. This article gives a brief synopsis of each, with examples for command-line invocation. About A comparsion between Fast API Uvicorn, Flask development server, Flask GUnicorn, Flask Waitress and . Aug 30, 2023 · A Side-by-Side Comparison of DRF (Django Rest Framework), FastAPI, and Flask Brief History and Rise of Python Web Frameworks The realm of web development has seen several seismic shifts since its inception. Whichever one you can get working first is the one to go with. Aug 4, 2024 · FastHTML is built on-top of the popular python libraries starlette, and uvicorn. FastHTML introduces Python types for common HTML elements integrated with HTMX which means you don't need to write html templates directly, and save a lot of time (in theory). This article assumes you’re using a sync framework like flask or Django and won’t explore the possibility of using the async/await pattern. So whilst in newer versions of Flask (2. Also you could swap out flask for one of the flask-like frameworks that use uvicorn instead of Gunicorn. Dec 16, 2020 · Gunicorn, uWSGI, or mod_wsgi? What the heck is a WSGI server? Why do I need one? Which one should I choose? Short answer: Use Gunicorn, unless you are deploying on Windows, in which case use mod Dec 16, 2020 · Gunicorn, uWSGI, or mod_wsgi? What the heck is a WSGI server? Why do I need one? Which one should I choose? Short answer: Use Gunicorn, unless you are deploying on Windows, in which case use mod Serve a ML model on a single machine with Flask + Gunicorn vs. js + pg by over 6x. Mar 11, 2022 · uvicorn is an ASGI (async server gateway interface) compatible web server. Flask The Python micro framework for building web applications. 80). So let’s get started! Starlette Starlette is a fast, lightweight . So that you have a better idea of what the test involves, below you can see the Flask and Aiohttp implementations of this service: import flask import json from sync_db import get_row app = flask. If I choose t Feb 25, 2021 · What is the difference between deploying FastAPI apps dockerized using Uvicorn and Tiangolo's Gunicorn+Uvicorn? And why do my results show that I get a better result when deploying only using Uvicorn Dec 20, 2023 · Exploring strategies for optimal Gunicorn, Uvicorn and Hypercorn configurations for Flask, Django, and FastAPI Sep 25, 2025 · Flask vs Falcon vs FastAPI benchmark. Deployment Concepts These examples run the server program (e. Uvicorn runs on windows and is an ASGI server. That's something that a framework like Starlette (or FastAPI) would provide on top. Oct 9, 2023 · Uvicorn and Gunicorn are powerful servers that can efficiently handle incoming requests, making them popular choices for hosting web applications built with Python frameworks like FastAPI, Django Jul 10, 2024 · So which framework should you choose? Since I have not personally used Django with async views, I'm going to focus on comparing Quart vs. Until recently Python has lacked a minimal low-level server/application interface for async frameworks. Learn practical implementation, best practices, and real-world examples. Uvicorn currently supports HTTP/1. The ASGI specification fills this gap, and means we're now able to start building a common set of tooling usable across all async frameworks. py. Note that Grinberg is comparing the overall performance of three parts: the Framework, the Jun 26, 2025 · Compare Python web servers: Uvicorn, Gunicorn, Daphne, and Hypercorn. Create an account for free. In particular all code (even standard library pure python code) seems to get slower if I use gunicorn. (by pallets) Uvicorn is a lightning-fast ASGI server implementation, using uvloop and httptools. Azure App Service is a fully managed web hosting service that supports Python apps hosted in a Linux server environment. But you will probably want to take care of some additional things, like: Security - HTTPS Running on startup Restarts Replication (the number of processes running) Memory Previous steps before starting I In this video, we dive deep into the differences between Gunicorn and Uvicorn, two popular Python web servers, and discuss their performance specifically with Django applications. Oct 18, 2025 · The lightning-fast ASGI server. Dec 5, 2021 · 不止一次的听过，FastAPI性能碾压Flask，直追Golang，不过一直没有测试过，今天闲着没事测试一下看看结果。不知道是哪里出了问题，结果大跌眼镜。 Mar 8, 2025 · Flask-Style Routing and Decorators All right, back to the routing and the decorators. Each of these tools has a… It integrates well with popular frameworks like Django and Flask, making it easy to deploy and manage applications. Starlette and Uvicorn work together seamlessly, allowing you to develop high-performance web applications with ease. The asgiref WsgiToAsgi adapter is recommended as it integrates with the event loop used for Flask’s Using async and await support. 1 and WebSockets. Flask("python-web-perf") @app. When you check the benchmarks, it is common to see several tools of different types compared as equivalent. Jan 10, 2025 · FastAPI + Uvicorn = Blazing Speed: The Tech Behind the Hype What is Uvicorn? Answer: Uvicorn is a very fast ASGI (Asynchronous Server Gateway Interface) server built on uvloop and httptools. If you installed connexion using connexion[uvicorn], you can run it using the run method. Jul 23, 2025 · uvicorn main:app --reload Output: Message: Hello World!!!! What is Gunicorn ? Gunicorn, a WSGI server, can be used alongside Uvicorn to serve FastAPI applications, despite not being specifically designed for ASGI. FastAPI + Uvicorn February 1, 2024 2024 · dev · flask, gunicorn, fastapi, uvicorn Gunicorn is a Python Web Server Gateway Interface (WSGI) HTTP server based on the pre-fork worker model. Flask vs FastAPI Performance Flask version upto 1. You can use the adapter by wrapping the Flask app, Uvicorn Uvicorn is a lightning-fast ASGI server, built on uvloop and httptools. Oct 22, 2024 · 本文针对那些有兴趣从Flask转移到FastAPI的人，比较和对比了Flask和FastAPI的常见模式。#FastAPIvsFlask@app. You can read more May 21, 2025 · A Rust HTTP server for Python applications. Settings Use the following options to configure Uvicorn, when running from the command line. This report provides a detailed comparison of the performance of a simple Flask web API implemented using different server frameworks: Gunicorn (WSGI), Uvicorn (ASGI), and Bjoern (WSGI). The oha tool was utilized to test 10,000 requests on the following frameworks, yielding the subsequent results: Flask (Gunicorn) Gunicorn vs Uvicorn：如何选择？ 选择 Gunicorn 还是 Uvicorn 主要取决于你的应用需求和工作负载类型。 使用 Gunicorn 的场景 传统同步 Web 应用：如果你的应用主要是基于 Django 或 Flask，并且不需要处理异步操作，那么 Gunicorn 是一个非常稳定和可靠的选择。 高稳定性和可靠性需求：Gunicorn 已被大量生产环境 Python frameworks benchmarksRead about the benchmark: The Methodic Check complete results for the latest benchmark here: Results (2022-03-14) Combined results This includes uvicorn[standard], which includes some dependencies (e. It includes: Simple web applications for both FastAPI and Flask. Nov 9, 2022 · As per documentation, FastAPI is built on top of Starlette which itself is built on top of Uvicorn. uvloop) needed for high performance serving. First, let’s briefly discuss how python handles concurrency and parallelism. Feb 11, 2022 · It’s important to compare FastAPI vs Flask by exploring the pros and cons of both. Uvicorn, while gaining popularity, may have limited support in some frameworks or may require additional configuration for smooth integration. However, its synchronous nature, processing one Feb 18, 2020 · I currently have a flask web application using uWSGI web server that implements the WSGI standard and need to migrate this app to uvicorn web server that implements the ASGI standard. Flask is literally the "do whatever you want" framework, whereas fastAPI has (at least what I consider) to be a pretty well-established FastAPI endpoint -> pydantic -> database (I use sqlalchemy) paradigm that's pretty damn useful for validation, doc creation, and things like pre and post processing using validators. UvicornWorker for production. Quickstart Install Jun 4, 2025 · The primary goal is to offer a clear, reproducible way to measure and contrast the request handling capabilities of FastAPI (using Uvicorn) and Flask (using Werkzeug's development server). 0. This… Sep 2, 2025 · FastAPI Since Workbench sessions run remotely behind a proxy, FastAPI applications on Workbench must use the ASGI root_path mechanism. FastAPI + psycopg2 + uvicorn, on the other hand, seemed to lag behind Express. For more information, see FastAPI’s Behind a Proxy documentation. 0 uses a synchronous model by default, which means it processes requests one at a time. The performance difference between the ASGI servers is small and arguably is not important in the grand scheme of things (aka going from flask to fast). Stuff like Starlette and Kenneth Reitz’s Responder framework use it. While trying to understand how I want to Dockerize the application I understood I want to implement Uvicorn without Gunicorn and to add a Uvicorn Uvicorn can run FastAPI application even with multiple workers, convenient during development thanks to the reload capability but even their documentation suggests to run with Gunicorn in production Workers Workers are pre-forked processes spawn by Gunicorn. May 21, 2023 · According to a benchmark study by Miguel Grinberg, FastAPI can be faster or slower than async Flask, depending on the web server and the Flask async type. When creating a Python app, you have two options: FastAPI vs Flask. Uvicorn is a lightning-fast ASGI server implementation, using uvloop and httptools. auk vzm kp 8ci ss otln0 p0 ga alqd3 igj