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CURLOPT_HSTS(3) curl_easy_setopt options CURLOPT_HSTS(3)
CURLOPT_HSTS - HSTS cache file name
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTS, char *filename);
Make the filename point to a file name to load an existing HSTS cache
from, and to store the cache in when the easy handle is closed. Setting
a file name with this option will also enable HSTS for this handle (the
equivalent of setting CURLHSTS_ENABLE with CURLOPT_HSTS_CTRL(3)).
If the given file does not exist or contains no HSTS entries at
startup, the HSTS cache will simply start empty. Setting the file name
to NULL or "" will only enable HSTS without reading from or writing to
If this option is set multiple times, libcurl will load cache entries
from each given file but will only store the last used name for later
The HSTS cache is saved to and loaded from a text file with one entry
per physical line. Each line in the file has the following format:
[host] is the domain name for the entry and the name is dot-prefixed if
it is an entry valid for all subdomains to the name as well or only for
the exact name.
[stamp] is the time (in UTC) when the entry expires and it uses the
format "YYYYMMDD HH:MM:SS".
Lines starting with "#" are treated as comments and are ignored. There
is currently no length or size limit.
NULL, no file name
HTTPS and HTTP
CURL *curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_HSTS, "/home/user/.hsts-cache");
Added in 7.74.0
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
CURLOPT_HSTS_CTRL(3), CURLOPT_ALTSVC(3), CURLOPT_RESOLVE(3),
libcurl 7.87.0 September 20, 2022 CURLOPT_HSTS(3)