HTTP Clients in Python

Requests is the familiar synchronous client: a simple API, sessions, and a large ecosystem of add-ons and mocking tools. It is built on urllib3, which handles connection pooling, retries and TLS, and which you can use directly when you want lower-level control with fewer dependencies. HTTPX offers a Requests-like API with both sync and async clients, optional HTTP/2 and strict timeouts by default. httpx2 is a fork of HTTPX maintained by the Pydantic team.

aiohttp is async-only and includes both a client and a server; it is mature and a good fit for high-concurrency crawlers and services already built on asyncio. As a rule of thumb, use Requests for scripts and sync apps, and HTTPX or aiohttp inside async frameworks such as FastAPI, where a blocking client would stall the event loop. yarl parses and builds URLs as immutable objects and is the URL type aiohttp uses.