---
name: "CURLOPT_SSLCERT_BLOB"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_SSLCERT_BLOB"
---

# CURLOPT\_SSLCERT\_BLOB(3)

SSL client certificate from memory blob

## NAME

CURLOPT\_SSLCERT\_BLOB - SSL client certificate from memory blob

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLCERT_BLOB,
                          struct curl_blob *stblob);
```

## DESCRIPTION

Pass a pointer to a curl\_blob structure, which contains (pointer and size) a client certificate. The format must be "P12" on Schannel. The format must be "P12" or "PEM" on OpenSSL. The format must be "DER" or "PEM" on mbedTLS. The format must be "PEM" on Rustls. The format must be specified with *[CURLOPT\_SSLCERTTYPE(3)](/CURLOPT_SSLCERTTYPE/3.md)*.

If the blob is initialized with the flags member of struct curl\_blob set to CURL\_BLOB\_COPY, the application does not have to keep the buffer around after setting this.

This option is an alternative to *[CURLOPT\_SSLCERT(3)](/CURLOPT_SSLCERT/3.md)* which instead expects a filename as input.

## DEFAULT

NULL

## PROTOCOLS

This functionality affects  all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. only

This option works only with the following TLS backends: OpenSSL, Rustls, Schannel, mbedTLS and wolfSSL

## EXAMPLE

```
extern char *certificateData; /* point to data */
extern size_t filesize; /* size of data */
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    struct curl_blob stblob;
    stblob.data = certificateData;
    stblob.len = filesize;
    stblob.flags = CURL_BLOB_COPY;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_SSLCERT_BLOB, &stblob);
    curl_easy_setopt(curl, CURLOPT_SSLCERTTYPE, "P12");
    curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in curl 7.71.0

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_KEYPASSWD**(3)](/CURLOPT_KEYPASSWD/3.md), [**CURLOPT\_SSLCERTTYPE**(3)](/CURLOPT_SSLCERTTYPE/3.md), [**CURLOPT\_SSLKEY**(3)](/CURLOPT_SSLKEY/3.md)