CURLOPT_SSL_OPTIONS(3) Library Functions Manual CURLOPT_SSL_OPTIONS(3)
NAME
CURLOPT_SSL_OPTIONS - SSL behavior options
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_OPTIONS, long bitmask);
DESCRIPTION
Pass a long with a bitmask to tell libcurl about specific SSL behaviors.
Available bits:
CURLSSLOPT_ALLOW_BEAST
Tells libcurl to not attempt to use any workarounds for a secu-
rity flaw in the SSL3 and TLS1.0 protocols. If this option is not
used or this bit is set to 0, the SSL layer libcurl uses may use
a work-around for this flaw although it might cause interoper-
ability problems with some (older) SSL implementations. WARNING:
avoiding this work-around lessens the security, and by setting
this option to 1 you ask for exactly that. This option is only
supported for Secure Transport and OpenSSL.
CURLSSLOPT_NO_REVOKE
Tells libcurl to disable certificate revocation checks for those
SSL backends where such behavior is present. This option is only
supported for Schannel (the native Windows SSL library), with an
exception in the case of Windows' Untrusted Publishers block list
which it seems cannot be bypassed. (Added in 7.44.0)
CURLSSLOPT_NO_PARTIALCHAIN
Tells libcurl to not accept "partial" certificate chains, which
it otherwise does by default. This option is only supported for
OpenSSL and fails the certificate verification if the chain ends
with an intermediate certificate and not with a root cert. (Added
in 7.68.0)
CURLSSLOPT_REVOKE_BEST_EFFORT
Tells libcurl to ignore certificate revocation checks in case of
missing or offline distribution points for those SSL backends
where such behavior is present. This option is only supported for
Schannel (the native Windows SSL library). If combined with
CURLSSLOPT_NO_REVOKE, the latter takes precedence. (Added in
7.70.0)
CURLSSLOPT_NATIVE_CA
Tell libcurl to use the operating system's native CA store for
certificate verification. This option is independent of other CA
certificate locations set at run time or build time. Those loca-
tions are searched in addition to the native CA store.
Works with wolfSSL on Windows, Linux (Debian, Ubuntu, Gentoo, Fe-
dora, RHEL), macOS, Android and iOS (added in 8.3.0); with GnuTLS
(added in 8.5.0) and with OpenSSL and its forks (LibreSSL, Bor-
ingSSL, etc) on Windows (Added in 7.71.0).
This works with rustls on Windows, macOS, Android and iOS. On
Linux it is equivalent to using the Mozilla CA certificate bun-
dle. When used with rustls _only_ the native CA store is con-
sulted, not other locations set at run time or build time. (Added
in 8.13.0)
CURLSSLOPT_AUTO_CLIENT_CERT
Tell libcurl to automatically locate and use a client certificate
for authentication, when requested by the server. This option is
only supported for Schannel (the native Windows SSL library).
Prior to 7.77.0 this was the default behavior in libcurl with
Schannel. Since the server can request any certificate that sup-
ports client authentication in the OS certificate store it could
be a privacy violation and unexpected. (Added in 7.77.0)
CURLSSLOPT_EARLYDATA
Tell libcurl to try sending application data as TLS1.3 early
data. This option is supported for GnuTLS, wolfSSL, quictls and
OpenSSL (but not BoringSSL or AWS-LC). It works on TCP and QUIC
connections using ngtcp2. This option works on a best effort ba-
sis, in cases when it wasn't possible to send early data the re-
quest is resent normally post-handshake. This option does not
work when using QUIC. (Added in 8.11.0 for GnuTLS and 8.13.0 for
wolfSSL, quictls and OpenSSL)
DEFAULT
0
PROTOCOLS
This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS,
POP3S, SMTPS etc.
All TLS backends support this option.
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
/* weaken TLS only for use with silly servers */
curl_easy_setopt(curl, CURLOPT_SSL_OPTIONS, (long)CURLSSLOPT_ALLOW_BEAST |
CURLSSLOPT_NO_REVOKE);
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
AVAILABILITY
Added in curl 7.25.0
RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred,
see libcurl-errors(3).
SEE ALSO
CURLOPT_PROXY_SSL_OPTIONS(3), CURLOPT_SSLVERSION(3), CURLOPT_SSL_CI-
PHER_LIST(3)
libcurl 2026-07-12 CURLOPT_SSL_OPTIONS(3)
Generated by dwww version 1.16 on Sat Oct 3 05:45:25 CEST 2026.