C++ HTTP Client Libraries: cpp-httplib vs cpr vs curlpp vs Boost.Beast

Every C++ application that calls REST APIs or downloads resources needs an HTTP client. But the C++ ecosystem offers radically different approaches: from header-only single-file libraries to C wrappers with C++ bindings to Boost-integrated solutions. This guide compares cpp-httplib, cpr, curlpp, and Boost.Beast across API design, dependency footprint, TLS support, and real-world performance.

Library Comparison

cpp-httplib: The Zero-Dependency Solution

cpp-httplib is a single httplib.h file that implements both HTTP client and server. Its API is deliberately Python-inspired — cli.Get(), cli.Post(), cli.set_bearer_token_auth() — making it immediately familiar to developers coming from Python’s requests or JavaScript’s fetch.

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#include <httplib.h>

// Simple GET request
httplib::Client cli("https://api.github.com");
cli.set_bearer_token_auth(getenv("GITHUB_TOKEN"));

auto res = cli.Get("/repos/yhirose/cpp-httplib");
if (res && res->status == 200) {
    std::cout << res->body << std::endl;
}

// POST with JSON
auto post_res = cli.Post("/issues", 
    R"({"title":"Bug report","body":"Description"})",
    "application/json");

The header-only design means zero build system configuration — just drop the file in your include path. cpp-httplib supports SSL via OpenSSL, mbedTLS, or BearSSL, multipart form uploads, range requests, redirect following, and connection keep-alive. Its limitation: no HTTP/2 support and no built-in async I/O (you’ll need to wrap calls in threads or pair with an event loop).

cpr: Curl for People

cpr wraps libcurl behind a modern C++ interface modeled after Python’s requests library. Every libcurl feature — HTTP/2, proxies, cookies, connection pooling, digest auth — is available through clean C++ methods.

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#include <cpr/cpr.h>

// GET with query parameters
auto r = cpr::Get(cpr::Url{"https://httpbin.org/get"},
    cpr::Parameters{{"key", "value"}, {"page", "1"}},
    cpr::Timeout{5000},
    cpr::Bearer{"token123"});

std::cout << r.status_code << ": " << r.text;

// Multipart file upload
auto upload = cpr::Post(cpr::Url{"https://httpbin.org/post"},
    cpr::Multipart{{"file", cpr::File{"/path/to/data.bin"}},
                   {"description", "test upload"}});

cpr handles session pooling automatically — multiple requests to the same host reuse the same TCP connection. Its async API wraps libcurl’s multi-handle:

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std::vector<cpr::AsyncResponse> responses;
for (auto& url : urls) {
    responses.emplace_back(cpr::GetAsync(cpr::Url{url}));
}
for (auto& future : responses) {
    auto r = future.get(); // blocks until complete
}

The downside: cpr links against libcurl (~4 MB shared library), and the build requires CMake + conan/vcpkg or manual libcurl installation.

curlpp: The Classic Curl Wrapper

curlpp wraps libcurl in a C++98-compatible, RAII-based interface. It’s the oldest of the four (first released in 2002) and retains a more verbose, curl-like programming model.

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#include <curlpp/cURLpp.hpp>
#include <curlpp/Easy.hpp>
#include <curlpp/Options.hpp>

curlpp::Cleanup cleaner;
curlpp::Easy request;

request.setOpt(curlpp::Options::Url("https://api.example.com/data"));
request.setOpt(curlpp::Options::HttpHeader({
    "Authorization: Bearer token123",
    "Accept: application/json"
}));

std::ostringstream response;
request.setOpt(curlpp::Options::WriteStream(&response));
request.perform();

std::cout << response.str();

curlpp’s strength is its maturity and coverage of libcurl’s vast option set. If you need SOCKS5 proxies, custom DNS resolution, or certificate pinning with specific openssl flags, curlpp exposes every knob. The trade-off: the API is less ergonomic than cpr or cpp-httplib, and the documentation is sparse compared to modern alternatives.

Boost.Beast: HTTP at the Protocol Level

Boost.Beast isn’t just an HTTP client — it’s an HTTP protocol implementation built on Boost.Asio. This means you get HTTP, WebSocket, and raw TCP within the same async framework. But it also means you write significantly more code.

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#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio/connect.hpp>
#include <boost/asio/ip/tcp.hpp>

namespace beast = boost::beast;
namespace http = beast::http;
namespace net = boost::asio;

// Setup
net::io_context ioc;
tcp::resolver resolver(ioc);
beast::tcp_stream stream(ioc);

auto const results = resolver.resolve("api.github.com", "443");
stream.connect(results);

// Build request
http::request<http::string_body> req{http::verb::get, "/repos/boostorg/beast", 11};
req.set(http::field::host, "api.github.com");
req.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);

// Send
http::write(stream, req);

// Receive
beast::flat_buffer buffer;
http::response<http::dynamic_body> res;
http::read(stream, buffer, res);

std::cout << res;

Beast’s power is its composability with the rest of Boost.Asio — you can build an HTTP client that shares the same I/O context as your WebSocket server, database connections, and timer callbacks. The cost is verbosity: even a simple GET requires ~20 lines of setup.

Performance Benchmarks

Benchmark: 10,000 sequential GET requests to a local nginx server (keep-alive enabled, 16-byte response body):

cpp-httplib leads in raw throughput because it avoids libcurl’s C-to-C++ translation layer. Boost.Beast is close behind despite its larger binary — Asio’s async engine is highly optimized. cpr and curlpp are nearly identical (both wrap libcurl), with cpr’s modern C++ generating slightly more efficient code paths. Boost.Beast’s binary size is 6x larger due to Boost’s template-heavy design, but this is a one-time cost amortized across all Beast-using components.

Choosing the Right Library

Choose cpp-httplib for greenfield projects where you want zero dependencies, minimal build complexity, and a requests-like API. Its header-only nature makes it ideal for single-developer projects, embedded systems, and quick prototypes. Drop it in and you’re done.

Choose cpr when you need HTTP/2, cookie jars, digest authentication, or proxy support out of the box. If your application already links against libcurl (common in Linux environments), cpr adds minimal overhead. The Python-requests API design makes it the easiest to learn.

Choose Boost.Beast when you’re already using Boost.Asio for networking, WebSockets, or timers. Beast’s composability is its killer feature — one I/O context for all async operations eliminates thread synchronization headaches. The verbosity pays off in large codebases where you need precise control over connection lifecycle.

Choose curlpp for legacy C++98 codebases that already depend on libcurl. For new projects, cpr provides the same libcurl features with a cleaner API.

Why Self-Host Your C++ API Infrastructure?

Running your own C++ HTTP client infrastructure within self-hosted services avoids third-party API gateway dependencies. When you control the HTTP client stack, you can fine-tune connection pooling, TLS certificate verification, and retry logic to match your exact service topology — impossible with managed API gateways that apply one-size-fits-all policies.

For guidance on C++ networking fundamentals, see our C++ networking libraries comparison. If your service communicates over WebSockets, refer to our C++ WebSocket libraries guide. For serialization formats commonly used with HTTP APIs, check our C++ serialization libraries comparison.

Error Handling and Resilience Patterns

HTTP clients in production face transient failures — DNS timeouts, connection resets, 502/503 responses, and TLS negotiation failures. Each library handles these differently.

cpp-httplib exposes error information through httplib::Error enumeration and res.error() method. Connection failures throw std::system_error when exceptions are enabled (via CPPHTTPLIB_NO_EXCEPTIONS define). For retry logic, you must implement it manually:

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httplib::Client cli("https://api.example.com");
for (int attempt = 0; attempt < 3; attempt++) {
    auto res = cli.Get("/data");
    if (res && res->status == 200) break;
    if (res && res->status >= 500) {
        std::this_thread::sleep_for(std::chrono::milliseconds(100 * (1 << attempt)));
        continue;
    }
    if (!res) {
        std::cerr << "Connection error: " << httplib::to_string(res.error()) << std::endl;
    }
}

cpr integrates with libcurl’s error buffer, providing detailed SSL and protocol-level error messages via r.error.message. cpr’s cpr::Timeout covers both connection and transfer timeouts, and cpr::ConnectTimeout isolates just the connection phase — critical for distinguishing DNS issues from slow servers.

Boost.Beast provides the most granular error handling through beast::error_code and beast::system_error. Beast separates connection errors (net::error), TLS errors (net::ssl::error), and HTTP protocol errors (http::error) into distinct categories, enabling precise retry logic. Combined with Asio’s steady_timer, you can implement exponential backoff without blocking threads.

For production deployments, always configure connection limits. cpp-httplib defaults to unlimited connections; set cli.set_keep_alive_max_count(100) and cli.set_keep_alive_timeout(30) to prevent socket exhaustion. cpr respects libcurl’s CURLOPT_MAXCONNECTS (default 5) for connection pooling, which is reasonable for most services.

FAQ

Does cpp-httplib support HTTPS?

Yes. Include #define CPPHTTPLIB_OPENSSL_SUPPORT before #include <httplib.h> and link against OpenSSL. You can alternatively use mbedTLS or BearSSL by defining CPPHTTPLIB_USE_MBEDTLS or CPPHTTPLIB_USE_BEARSSL. The library handles TLS transparently — just use https:// URLs.

Why would I use Beast instead of cpr when Beast requires more code?

Beast integrates with Boost.Asio’s async model. If your application already uses Asio for networking, database connections, or timers, adding Beast means zero additional I/O threads — everything runs on the same io_context. With cpr, you’d need separate threads or an async wrapper, which adds synchronization complexity. The extra code pays for itself in multi-service architectures.

Can I use these libraries in a header-only fashion?

cpp-httplib and Boost.Beast are fully header-only. cpr requires compiling a shared library (it links against libcurl). curlpp also requires compilation. For header-only deployments, cpp-httplib is the simplest choice.

How do these handle connection timeouts?

cpp-httplib: cli.set_connection_timeout(5, 0) (5 seconds). cpr: cpr::Timeout{5000} (milliseconds, covers both connect and read). curlpp: request.setOpt(curlpp::Options::ConnectTimeout(5)). Beast: stream.expires_after(std::chrono::seconds(5)).

Are these libraries thread-safe?

cpp-httplib: Client instances are not thread-safe; create one per thread. cpr: sessions are not thread-safe, but creating separate cpr::Session objects per thread works. curlpp: same pattern — one Easy handle per thread. Beast: fully thread-safe when using net::strand or separate io_context instances per thread.

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