curl is both a shell command and a client library
curl is the familiar command that fetches a URL, but the project is broader than an HTTP terminal utility. Its README lists web, file-transfer, mail, directory, messaging, and remote-login protocols. The same repository contains libcurl, a C library applications use for client-side transfers. That split matters when comparing alternatives: HTTPie competes with the command's interactive experience, while an embedded networking library competes with libcurl.
The command works well in scripts because it exposes redirects, headers, authentication, proxies, cookies, uploads, certificates, rate limits, and output formatting without requiring application code. libcurl adds persistent connections, IPv6, Unix sockets, DNS-over-HTTPS, WebSockets, and synchronous or event-driven APIs. Our checkout was 18.2 MB with about 312,680 source lines, evidence that the small command name sits on a substantial portability and protocol codebase.
Binary installation is simple; a source build is a feature decision
Most users should install curl through their operating system or download a published binary. The project's source guide intentionally starts elsewhere: it asks builders to choose CMake or autotools, pick a TLS backend, and decide which optional capabilities belong in the result. Those decisions affect certificate stores, compression, HTTP/2, HTTP/3, SSH, international domain names, and asynchronous DNS.
A source checkout can use OpenSSL, GnuTLS, mbedTLS, Rustls, Schannel, wolfSSL, or AmiSSL depending on the platform and desired build. Several backends can coexist in some configurations, but HTTP/3 cannot be combined with the MultiSSL feature. The 4,451 files we inspected also included 16 CI workflow files, a Dockerfile, and a tests directory. That machinery reflects the number of combinations maintainers need to exercise.
What happened when we ran it
Our fresh Debian sandbox attempted the CMake configuration at commit 6017e6f. It failed with exit code 1 after 8 seconds. CMake could not find Zstd, NGHTTP2, or Libidn2 development files, then treated missing Libpsl headers and its library as the fatal error. Configuration remained incomplete, so there was no compiled executable or library to test.
We did not run a build or test suite after that 8-second failure. The log does not say the source is broken, nor does it show whether installing Libpsl alone would have completed the chosen configuration. It shows that this feature selection was not self-contained in the fresh container. The install guide documents the relevant choice: curl uses libpsl by default, and builders can install it or disable that support.
libcurl rewards callers that understand handles and connection reuse
The easy interface starts with a handle, sets options, performs a transfer, and cleans up. Options stay attached to the handle until changed or reset. Reusing it matters because libcurl keeps connections for later requests; immediately destroying every handle throws that advantage away. The option index exceeds 300 entries, which is useful when a product needs precise transport control and excessive when it only needs a pleasant JSON request syntax.
Parallel work uses the multi interface. One multi handle owns several easy handles and lets the application drive transfers alongside its own file descriptors. The documentation warns that completed transfers remain attached until the caller removes and cleans them up. It also names blocking exceptions, including some name-resolution configurations, file://, and TELNET. A team adopting libcurl should wrap these lifecycles once, test the wrapper, and stop scattering raw option calls across business code.
Static linking exposes the full dependency chain
Dynamic builds let the platform loader resolve third-party libraries. A fully static libcurl build must supply each dependency and often the dependencies behind those dependencies. The official guide describes that job bluntly as difficult because the required link set varies by platform and version. This is a real reason to walk away if a single-file binary is mandatory and curl's wide feature set is unnecessary.
Our missing Zstd, NGHTTP2, Libidn2, and Libpsl checks illustrate the same modularity from the other side. A product can compile out features it does not need, but it must understand the resulting capability list. Record curl --version output in support reports because two machines with a command named curl may use different TLS backends and protocol features even when their command syntax matches.
Current maintenance matches curl's infrastructure role
GitHub reported a push on August 26, 2026, 42,686 stars, and 38 combined open issues and pull requests. The latest release was 8.21.0, published June 24, 2026. A low combined queue beside same-day repository activity is a better health signal than the release date alone, especially for software whose changes are often transport fixes rather than visible interface additions.
The documentation is part of the product: a full command manual, the Everything curl book, per-function libcurl pages, build instructions, and private security reporting all have clear homes. That depth cannot make every build combination easy, but it makes the choices inspectable. Use the packaged command almost by default. Use libcurl when you truly need its portability and transport control, and build it yourself only when the exact enabled features belong to your product requirements.