Why I built a new HTTP client after working on HTTPX ​

A bit of history ​

In 2022, I built a small experimental HTTP client called aioreq. It was async-only, zero-dependency, and mostly an educational project.

A few months later, I joined the HTTPX (encode) team and became one of the maintainers, working on both HTTPX and httpcore (its underlying engine). That’s where I gained real experience and started to see the bigger picture behind HTTP clients.

I also built tools on top of HTTPX, like hishel, a caching layer that ended up getting some real adoption.

The problem ​

Over time, HTTPX development slowed down. Reviews and releases became infrequent, and I gradually stepped away.

httpcore, which is more critical (it is the engine), had unresolved issues that directly affected users.

So I built httpx-aiohttp - an adapter that swaps out httpcore for aiohttp while keeping HTTPX’s API intact. The OpenAI and Anthropic Python SDKs both adopted it in production.

The core issue ​

Most HTTP clients mix two very different concerns:

  • HTTP protocol logic (cookies, redirects, headers, caching - RFC-level behavior)
  • Transport layer (TCP, TLS, DNS, HTTP/1.1 vs HTTP/2, etc.)

This leads to questions like:

  • “Does this client support HTTP/2?”
  • “Does it have DNS caching?”
  • “Can I swap the TLS backend?”

or statements like:

  • “This HTTP client is slow”
  • “This HTTP client’s connection pooling sucks”

These are transport questions - but they’re tightly coupled to the client itself.

How Zapros is designed differently ​

I built Zapros around a strict separation:

  • A pure HTTP layer that implements the protocol
  • A pluggable transport layer responsible only for sending/receiving bytes

This means:

  • The HTTP layer stays focused on protocol correctness: cookies, redirects, headers, caching.
  • Transport concerns - connection pooling, TLS, DNS, HTTP/2 - live in one place and can be swapped or improved independently.
  • Testing is straightforward: mock the transport, not the client.
  • The transport can be replaced entirely - including with a WASM-compatible one for browser environments.

Current state ​

Zapros is at v0.6.0 - usable and under active development. The core API is stable; some advanced features are still being added. Feedback welcome.