curl_version_info(3) Library Functions Manual curl_version_info(3)
NAME
curl_version_info - returns runtime libcurl version info
SYNOPSIS
#include <curl/curl.h>
curl_version_info_data *curl_version_info(CURLversion age);
DESCRIPTION
Returns a pointer to a filled in static struct with information about
various features in the running version of libcurl. age should be set to
the version of this functionality by the time you write your program.
This way, libcurl always returns a proper struct that your program un-
derstands, while programs in the future might get a different struct.
CURLVERSION_NOW is the most recent one for the library you have in-
stalled:
data = curl_version_info(CURLVERSION_NOW);
Applications should use this information to judge if things are possible
to do or not, instead of using compile-time checks, as dynamic/DLL li-
braries can be changed independent of applications.
This function can alter the returned static data as long as
curl_global_init(3) has not been called. It is therefore not thread-safe
before libcurl initialization occurs.
The curl_version_info_data struct looks like this
typedef struct {
CURLversion age; /* see description below */
const char *version; /* human readable string */
unsigned int version_num; /* numeric representation */
const char *host; /* human readable string */
int features; /* bitmask, see below */
char *ssl_version; /* human readable string */
long ssl_version_num; /* not used, always zero */
const char *libz_version; /* human readable string */
const char *const *protocols; /* protocols */
/* when 'age' is CURLVERSION_SECOND or higher, the members below exist */
const char *ares; /* human readable string */
int ares_num; /* number */
/* when 'age' is CURLVERSION_THIRD or higher, the members below exist */
const char *libidn; /* human readable string */
/* when 'age' is CURLVERSION_FOURTH or higher (>= 7.16.1), the members
below exist */
int iconv_ver_num; /* '_libiconv_version' if iconv support enabled */
const char *libssh_version; /* human readable string */
/* when 'age' is CURLVERSION_FIFTH or higher (>= 7.57.0), the members
below exist */
unsigned int brotli_ver_num; /* Numeric Brotli version
(MAJOR << 24) | (MINOR << 12) | PATCH */
const char *brotli_version; /* human readable string. */
/* when 'age' is CURLVERSION_SIXTH or higher (>= 7.66.0), the members
below exist */
unsigned int nghttp2_ver_num; /* Numeric nghttp2 version
(MAJOR << 16) | (MINOR << 8) | PATCH */
const char *nghttp2_version; /* human readable string. */
const char *quic_version; /* human readable quic (+ HTTP/3) library +
version or NULL */
/* when 'age' is CURLVERSION_SEVENTH or higher (>= 7.70.0), the members
below exist */
const char *cainfo; /* the built-in default CURLOPT_CAINFO, might
be NULL */
const char *capath; /* the built-in default CURLOPT_CAPATH, might
be NULL */
/* when 'age' is CURLVERSION_EIGHTH or higher (>= 7.71.0), the members
below exist */
unsigned int zstd_ver_num; /* Numeric Zstd version
(MAJOR << 24) | (MINOR << 12) | PATCH */
const char *zstd_version; /* human readable string. */
/* when 'age' is CURLVERSION_NINTH or higher (>= 7.75.0), the members
below exist */
const char *hyper_version; /* human readable string. */
/* when 'age' is CURLVERSION_TENTH or higher (>= 7.77.0), the members
below exist */
const char *gsasl_version; /* human readable string. */
/* when 'age' is CURLVERSION_ELEVENTH or higher (>= 7.87.0), the members
below exist */
const char *const *feature_names; /* Feature names. */
/* when 'age' is CURLVERSION_TWELFTH or higher (>= 8.8.0), the members
below exist */
const char *const *rtmp_version; /* human readable string */
} curl_version_info_data;
age describes what the age of this struct is. The number depends on how
new the libcurl you are using is. You are however guaranteed to get a
struct that you have a matching struct for in the header, as you tell
libcurl your "age" with the input argument.
version is just an ASCII string for the libcurl version.
version_num is a 24 bit number created like this: <8 bits major number>
| <8 bits minor number> | <8 bits patch number>. Version 7.9.8 is there-
fore returned as 0x070908.
host is an ASCII string showing what host information that this libcurl
was built for. As discovered by a configure script or set by the build
environment.
features is a bit mask representing available features. It can have
none, one or more bits set. The use of this field is deprecated: use
feature_names instead. The feature names description below lists the as-
sociated bits.
feature_names is a pointer to an array of string pointers, containing
the names of the features that libcurl supports. The array is terminated
by a NULL entry. See the list of features names below.
ssl_version is an ASCII string for the TLS library name + version used.
If libcurl has no SSL support, this is NULL. For example "Schannel",
"Secure Transport" or "OpenSSL/1.1.0g". For MultiSSL builds the string
contains all SSL backend names and the inactive backend names are in
parentheses. For example "(OpenSSL/3.0.8) Schannel" or "OpenSSL/3.0.8
(Schannel)".
ssl_version_num is always 0.
libz_version is an ASCII string (there is no numerical version). If
libcurl has no libz support, this is NULL.
protocols is a pointer to an array of char * pointers, containing the
names protocols that libcurl supports (using lowercase letters). The
protocol names are the same as would be used in URLs. The array is ter-
minated by a NULL entry.
FEATURES
alt-svc
features mask bit: CURL_VERSION_ALTSVC
HTTP Alt-Svc parsing and the associated options (Added in 7.64.1)
AsynchDNS
features mask bit: CURL_VERSION_ASYNCHDNS
libcurl was built with support for asynchronous name lookups,
which allows more exact timeouts (even on Windows) and less
blocking when using the multi interface. (added in 7.10.7)
brotli features mask bit: CURL_VERSION_BROTLI
supports HTTP Brotli content encoding using libbrotlidec (Added
in 7.57.0)
asyn-rr
features mask bit: non-existent
libcurl was built to use c-ares for EXPERIMENTAL HTTPS resource
record resolves, but uses the threaded resolver for "normal" re-
solves (Added in 8.12.0)
Debug features mask bit: CURL_VERSION_DEBUG
libcurl was built with debug capabilities (added in 7.10.6)
ECH features mask bit: non-existent
libcurl was built with ECH support (experimental, added in 8.8.0)
gsasl features mask bit: CURL_VERSION_GSASL
libcurl was built with libgsasl and thus with some extra
SCRAM-SHA authentication methods. (added in 7.76.0)
GSS-API
features mask bit: CURL_VERSION_GSSAPI
libcurl was built with support for GSS-API. This makes libcurl
use provided functions for Kerberos and SPNEGO authentication. It
also allows libcurl to use the current user credentials without
the app having to pass them on. (Added in 7.38.0)
HSTS features mask bit: CURL_VERSION_HSTS
libcurl was built with support for HSTS (HTTP Strict Transport
Security) (Added in 7.74.0)
HTTP2 features mask bit: CURL_VERSION_HTTP2
libcurl was built with support for HTTP2. (Added in 7.33.0)
HTTP3 features mask bit: CURL_VERSION_HTTP3
HTTP/3 and QUIC support are built-in (Added in 7.66.0)
HTTPS-proxy
features mask bit: CURL_VERSION_HTTPS_PROXY
libcurl was built with support for HTTPS-proxy. (Added in
7.52.0)
HTTPSRR
features mask bit: non-existent
libcurl was built with EXPERIMENTAL support for HTTPS resource
records (Added in 8.12.0)
IDN features mask bit: CURL_VERSION_IDN
libcurl was built with support for IDNA, domain names with inter-
national letters. (Added in 7.12.0)
IPv6 features mask bit: CURL_VERSION_IPV6
supports IPv6
Kerberos
features mask bit: CURL_VERSION_KERBEROS5
supports Kerberos V5 authentication for FTP, IMAP, LDAP, POP3,
SMTP and SOCKSv5 proxy. (Added in 7.40.0)
Largefile
features mask bit: CURL_VERSION_LARGEFILE
libcurl was built with support for large files. (Added in 7.11.1)
libz features mask bit: CURL_VERSION_LIBZ
supports HTTP deflate using libz (Added in 7.10)
MultiSSL
features mask bit: CURL_VERSION_MULTI_SSL
libcurl was built with multiple SSL backends. For details, see
curl_global_sslset(3). (Added in 7.56.0)
NTLM features mask bit: CURL_VERSION_NTLM
supports HTTP NTLM (added in 7.10.6)
NTLM_WB
features mask bit: CURL_VERSION_NTLM_WB
libcurl was built with support for NTLM delegation to a winbind
helper. (Added in 7.22.0) This feature was removed from curl in
8.8.0.
PSL features mask bit: CURL_VERSION_PSL
libcurl was built with support for Mozilla's Public Suffix List.
This makes libcurl ignore cookies with a domain that is on the
list. (Added in 7.47.0)
SPNEGO features mask bit: CURL_VERSION_SPNEGO
libcurl was built with support for SPNEGO authentication (Simple
and Protected GSS-API Negotiation Mechanism, defined in RFC
2478.) (added in 7.10.8)
SSL features mask bit: CURL_VERSION_SSL
supports SSL (HTTPS/FTPS) (Added in 7.10)
SSLS-EXPORT
features mask bit: non-existent
libcurl was built with SSL session import/export support (experi-
mental, added in 8.12.0)
SSPI features mask bit: CURL_VERSION_SSPI
libcurl was built with support for SSPI. This is only available
on Windows and makes libcurl use Windows-provided functions for
Kerberos, NTLM, SPNEGO and Digest authentication. It also allows
libcurl to use the current user credentials without the app hav-
ing to pass them on. (Added in 7.13.2)
threadsafe
features mask bit: CURL_VERSION_THREADSAFE
libcurl was built with thread-safety support (Atomic or SRWLOCK)
to protect curl initialization. (Added in 7.84.0) See
libcurl-thread(3)
TLS-SRP
features mask bit: CURL_VERSION_TLSAUTH_SRP
libcurl was built with support for TLS-SRP (in one or more of the
built-in TLS backends). (Added in 7.21.4)
TrackMemory
features mask bit: CURL_VERSION_CURLDEBUG
libcurl was built with memory tracking debug capabilities. This
is mainly of interest for libcurl hackers. (added in 7.19.6)
Unicode
features mask bit: CURL_VERSION_UNICODE
libcurl was built with Unicode support on Windows. This makes
non-ASCII characters work in filenames and options passed to
libcurl. (Added in 7.72.0)
UnixSockets
features mask bit: CURL_VERSION_UNIX_SOCKETS
libcurl was built with support for Unix domain sockets. (Added
in 7.40.0)
zstd features mask bit: CURL_VERSION_ZSTD
supports HTTP zstd content encoding using zstd library (Added in
7.72.0)
no name
features mask bit: CURL_VERSION_CONV
libcurl was built with support for character conversions provided
by callbacks. Always 0 since 7.82.0. (Added in 7.15.4, depre-
cated.)
no name
features mask bit: CURL_VERSION_GSSNEGOTIATE
supports HTTP GSS-Negotiate (added in 7.10.6, deprecated in
7.38.0)
no name
features mask bit: CURL_VERSION_KERBEROS4
supports Kerberos V4 (when using FTP). Legacy bit. Deprecated
since 7.33.0.
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
int main(void)
{
curl_version_info_data *ver = curl_version_info(CURLVERSION_NOW);
printf("libcurl version %u.%u.%u\n",
(ver->version_num >> 16) & 0xff,
(ver->version_num >> 8) & 0xff,
ver->version_num & 0xff);
}
AVAILABILITY
Added in curl 7.10
RETURN VALUE
A pointer to a curl_version_info_data struct.
SEE ALSO
curl_version(3)
libcurl 2026-07-12 curl_version_info(3)
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