curl_version_info(3)

Okay bestie, this is curl_version_info(3) from the Library Functions Manual — aka the runtime vibe check for libcurl. 💅✨

💖 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 info about various features in the running version of libcurl. Set age to the version of this functionality at the time you write your program. That way, libcurl always returns a proper struct that your program understands, while programs in the future might get a different struct. CURLVERSION_NOW is the most recent one for the library you have installed:

  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 libraries 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. No cap.

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 — says 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, because you tell libcurl your “age” with the input argument. 🫶
version — just an ASCII string for the libcurl version.
version_num — a 24-bit number made like this: <8 bits major number> | <8 bits minor number> | <8 bits patch number>. Version 7.9.8 is therefore returned as 0x070908. 🎀
host — an ASCII string showing what host information this libcurl was built for. As discovered by a configure script or set by the build environment.
features — 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 associated bits.
feature_names — 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 feature names below. 👑
ssl_version — 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 — always 0.
libz_version — an ASCII string (there is no numerical version). If libcurl has no libz support, this is NULL.
protocols — a pointer to an array of char * pointers, containing the names of protocols that libcurl supports (using lowercase letters). The protocol names are the same as would be used in URLs. The array is terminated by a NULL entry. 🌈

✨ FEATURES ✨

Okay bestie, this is the fun part — this is where libcurl shows you literally everything it can do. Each feature has a name, its little features mask bit, and the tea on what it means. Some of these are just vibes, no mask bit at all (we'll get to those). Scroll slow, there's a lot 💅

alt-svc — features mask bit: CURL_VERSION_ALTSVC HTTP Alt-Svc parsing and the associated options (Added in 7.64.1)
AppleSecTrust — features mask bit: non-existent libcurl was built with support for Apple's SecTrust service to verify server certificates (Added in 8.17.0).
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.
brotli — features mask bit: CURL_VERSION_BROTLI supports HTTP Brotli content encoding using libbrotlidec
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" resolves (Added in 8.12.0)
Debug — features mask bit: CURL_VERSION_DEBUG libcurl was built with debug capabilities
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.
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.
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.
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 international letters.
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.
Largefile — features mask bit: CURL_VERSION_LARGEFILE libcurl was built with support for large files.
libz — features mask bit: CURL_VERSION_LIBZ supports HTTP deflate using libz
MultiSSL — features mask bit: CURL_VERSION_MULTI_SSL libcurl was built with multiple SSL backends. For details, see curl_global_sslset(3).
NTLM — features mask bit: CURL_VERSION_NTLM supports HTTP NTLM
NTLM_WB — features mask bit: CURL_VERSION_NTLM_WB libcurl was built with support for NTLM delegation to a winbind helper. 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.
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.)
SSL — features mask bit: CURL_VERSION_SSL supports SSL (HTTPS/FTPS)
SSLS-EXPORT — features mask bit: non-existent libcurl was built with SSL session import/export support (experimental, 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 having to pass them on.
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).
TrackMemory — features mask bit: CURL_VERSION_CURLDEBUG libcurl was built with memory tracking debug capabilities. This is mainly of interest for libcurl hackers.
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.
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. Deprecated.
no name — features mask bit: CURL_VERSION_GSSNEGOTIATE supports HTTP GSS-Negotiate. Deprecated.
no name — features mask bit: CURL_VERSION_KERBEROS4 supports Kerberos V4 (when using FTP). Legacy bit. Deprecated since 7.33.0.

Heads up bestie: those last three have literally no name, and the first two of those are deprecated, and one of them is always 0 since 7.82.0. And CURL_VERSION_KERBEROS4 is legacy and deprecated since 7.33.0 — she's a museum piece 🏛️

🦋 PROTOCOLS 🦋

This functionality affects all supported protocols

🌸 EXAMPLE 🌸

okay so like a little taste test, here's you getting the version numbers out of that version_num field 🎀

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)

and that's the whole page bestie, you ate that 💅✨ This glow-up came to you from the libcurl fam — page curl_version_info(3), dated 2026-10-12, no cap 🫶🌸

📦 where this page comes from

fedora 44: libcurl-devel 8.18.0-14.fc44 · curl
fedora 44: libcurl-devel 8.18.0-14.fc44 · curl
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-06: a language model's rewrite of the original, under its terms