aiohttp
Asynchronous HTTP client and server framework for Python asyncio. Provides both an async HTTP client (aiohttp.ClientSession) for making concurrent HTTP requests and an async web server for building APIs. Supports WebSockets (both client and server), streaming, middleware, and connection pooling. Predates FastAPI — used by applications needing both client and server HTTP in one library.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Apache 2.0 licensed. SSL verification enabled by default. Trust only verified certificates in production. Regular security updates from aio-libs maintainers.
⚡ Reliability
Best When
You need both async HTTP client and server in the same library, especially for WebSocket support or high-concurrency scraping pipelines.
Avoid When
You only need an async HTTP client — httpx is easier to use. For web APIs, FastAPI has better developer experience and ecosystem.
Use Cases
- • Make concurrent async HTTP requests in Python agent pipelines — download multiple URLs simultaneously
- • Build WebSocket-based agent communication servers with aiohttp's WebSocket server support
- • Implement high-concurrency agent web scrapers that make thousands of concurrent HTTP requests
- • Create lightweight async HTTP servers when FastAPI's Pydantic/OpenAPI overhead is unnecessary
- • Build agent HTTP clients with session management, cookie handling, and connection pooling
Not For
- • Simple async HTTP clients in modern Python — httpx has better ergonomics and drop-in requests compatibility
- • Production REST APIs — FastAPI provides better validation, documentation, and ecosystem
- • CPU-bound workloads — async doesn't help with CPU parallelism; use multiprocessing
Interface
Authentication
Local library — no authentication required. Apache 2.0 licensed.
Pricing
Apache 2.0 licensed. Zero cost.
Agent Metadata
Known Gotchas
- ⚠ Must use async with aiohttp.ClientSession() as session: — create ONE session per application, not per request; sessions manage connection pools
- ⚠ aiohttp.ClientSession is NOT thread-safe — create in event loop context; for multi-threaded use, create separate sessions per thread
- ⚠ Response body must be read within the context manager: async with session.get(url) as resp: data = await resp.json() — reading after context exits fails
- ⚠ SSL verification disabled by default warning: use ssl=False only for development; use ssl=aiohttp.SSLContext for custom CA certs in production
- ⚠ Timeouts: aiohttp.ClientTimeout(total=30, connect=10, sock_read=20) — fine-grained timeout control; default has no timeout (dangerous)
- ⚠ Connector limits: aiohttp.TCPConnector(limit=100) limits concurrent connections — prevent overwhelming targets with connection pooling
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for aiohttp.
Scores are editorial opinions as of 2026-03-06.