Libraries

The repository builds two static C libraries and one shared library:

Library	Source	Public?	Description
libcurl	lib/	Yes (include/curl/)	The protocol-rich URL transfer library. The flagship product.
libcurlu	subset of lib/ (URL API + curlx)	Standalone optional build	A trimmed library exposing only the URL parser. Built when only the URL API is wanted.
curlx	lib/curlx/	No (internal only)	Internal portability/utility library, statically linked into libcurl and the curl tool.

Pages:

• libcurl — internal architecture of the main library
• curlx — the internal portability layer

The runtime behaviour of libcurl (transfer engine, connection management, protocol handlers, TLS, HTTP/2, HTTP/3, authentication, cookies, etc.) is documented under Systems, Features, and API.