Getting started

This page walks through cloning the repository, building curl and libcurl from source, running the test suite, and pointing the resulting binary at a sample URL. The complete reference for every build option lives in docs/INSTALL.md and docs/INSTALL-CMAKE.md; this page covers the path most contributors take.

Prerequisites

Requirement	Minimum version	Notes
C compiler	C89-capable	Must support 64-bit integers and stdint.h. GCC, Clang, MSVC, Intel, and many more are exercised in CI
GNU autoconf	2.59	Only needed when building from a git checkout (autoreconf -fi to bootstrap)
GNU automake	1.7	Same
GNU libtool	1.4.2	Same
CMake	3.18	Alternative to Autotools; required on Windows
perl	5.8 (5.22 on Windows)	Used by the test suite, doc tooling, and several build scripts
pkg-config	recent	Recommended for finding TLS/SSH/compression dependencies
A TLS backend	one of many	OpenSSL ≥ 3.0.0, GnuTLS ≥ 3.6.5, mbedTLS ≥ 3.2.0, wolfSSL ≥ 5.0.0, Schannel, Rustls, Apple SecTrust, …

The full list of supported third-party library versions is in docs/INTERNALS.md.

Build with Autotools (POSIX)

git clone https://github.com/curl/curl
cd curl
autoreconf -fi              # only when building from git
./configure --with-openssl  # pick a TLS backend
make
make test                   # optional, builds and runs ~1995 tests
sudo make install

If configure cannot find OpenSSL automatically, point it at a prefix:

./configure --with-openssl=/opt/openssl
# or
PKG_CONFIG_PATH=/opt/openssl/lib/pkgconfig ./configure --with-openssl

To explicitly build without TLS:

./configure --without-ssl

The configure flag namespace is built up by configure.ac and the macros under m4/. configure --help lists all options.

Build with CMake

cmake -B bld -DCURL_USE_OPENSSL=ON
cmake --build bld -j
ctest --test-dir bld           # CMake-driven test wrapper
cmake --install bld

CMake variables for picking dependencies follow the pattern CURL_USE_<LIB>=ON|OFF (e.g. CURL_USE_GNUTLS, CURL_USE_WOLFSSL, CURL_USE_LIBSSH). The full set is in CMakeLists.txt. CMake is the only build system supported on Windows.

Disabling features

curl is highly configurable. For embedded systems and constrained builds, see docs/CURL-DISABLE.md and the CURL_DISABLE_* macros in lib/curl_setup.h. Examples:

./configure --disable-ftp --disable-smtp --disable-pop3 --disable-imap --disable-ldap

Each disabled feature compiles out of both libcurl and the CLI. Combinations are exercised in the linux.yml and non-native.yml CI matrices.

Verifying the build

src/curl --version
src/curl https://example.com/

curl --version prints the libcurl version, the SSL backend, the resolver, the SSH backend, the QUIC backend, and a feature flag list. The same data is available programmatically via curl_version_info() (lib/version.c).

Running the test suite

make test                          # runs the protocol tests under tests/
( cd tests && ./runtests.pl 1)     # run a single test by number
( cd tests && ./runtests.pl -t)    # torture mode
( cd tests && ./runtests.pl -p)    # show test output

The functional tests live in tests/data/test* (one file per test, see docs/runtests.md), the unit tests in tests/unit/ and tests/tunit/, and the test driver in tests/runtests.pl. The Perl-based harness spins up its own HTTP, FTP, IMAP, POP3, SMTP, TFTP, and SSH servers under tests/server/, then runs curl against them. See Testing for the testing model.

Sample programs

Reference C programs live under docs/examples/ (~129 small programs). Each demonstrates one feature: simple.c is a one-line GET, multi-app.c shows the multi interface, https.c shows TLS configuration, and so on. They are built into the test suite via docs/examples/Makefile.inc.

Container build

A Dockerfile at the repo root produces an image suitable for running the test suite. The official curl Docker image (curlimages/curl) is built from the same source but configured for distribution.

Where to next?

• Read Architecture to see how curl_easy_perform() fans out into the multi loop, connection cache, and filter chain
• Read How to contribute → Development workflow for the commit/PR process
• Read How to contribute → Testing before adding code