Files
cpp-httplib/docs-src/pages/en/cookbook/c15-compression.md
T
yhirose 9bfd2ddf1c Fix README and docs pages that no longer match the code
Bring the READMEs and the docs pages (en and ja) in line with the
current header:

- Fix the client sample that does not compile, the Transfer-Encoding
  statement for default headers, the verifier callback comment, the
  thread pool spawn rule, the sanitize_filename description, and the
  inverted Accept-Encoding sentence.
- Describe recent behaviour: TLS errors behind Read/Write failures,
  Host validation, Connection: close for a body without length,
  content_reader rules, refused CONNECT, WebSocketClient proxies,
  CPPHTTPLIB_INTERIM_RESPONSE_MAX_COUNT, the SSE event size limit, and
  the payload limit of the Stream API.
- Complete the API references of WebSocket, WebSocketClient and the
  stream:: helpers, and the SSE reconnect rules.
- Fix cookbook pages: keychain loading on every backend, received Close
  status, a multipart sample that trusted the client's file name, an
  echo sample that sent binary as text, SNI, pre-request handler scope,
  stop() with WebSocket handlers, and the thread pool notes.
- Restore the mutex in the LLM app's Chapter 5 code.
2026-10-18 10:13:57 -04:00

1.8 KiB

title, order, status
title order status
C15. Enable Compression 15 draft

cpp-httplib supports compression when sending and decompression when receiving. You just need to build it with zlib, Brotli, or Zstd enabled.

Build-time setup

To use compression, define these macros before including httplib.h:

#define CPPHTTPLIB_ZLIB_SUPPORT    // gzip / deflate
#define CPPHTTPLIB_BROTLI_SUPPORT  // brotli
#define CPPHTTPLIB_ZSTD_SUPPORT    // zstd
#include <httplib.h>

You'll also need to link against zlib, brotli, or zstd, whichever you enabled.

Compress the request body

httplib::Client cli("https://api.example.com");
cli.set_compress(true);

std::string big_payload = build_payload();
auto res = cli.Post("/api/data", big_payload, "application/json");

With set_compress(true), the body of POST, PUT, or PATCH requests is compressed before sending. The encoding is the first one enabled in your build, in the order Brotli, gzip, Zstd. The server needs to handle compressed bodies too.

Decompress the response

httplib::Client cli("https://api.example.com");
cli.set_decompress(true); // on by default

auto res = cli.Get("/api/data");
std::cout << res->body << std::endl;

With set_decompress(true), the client automatically decompresses responses that arrive with Content-Encoding: gzip or similar. res->body contains the decompressed data.

It's on by default, so normally you don't need to do anything. Set it to false only if you want the raw compressed bytes.

Warning: If you build without any compression library, set_compress(true) leaves the request uncompressed. And a response compressed with an encoding your build lacks makes the request fail with Error::UnsupportedContentEncoding. If compression isn't working, check the macro definitions first.