Optional libraries provide additional feature capabilities to the modules.

feature required libs '''what?'''
auth-crypt crypt() from libc/libcrypt provides htpasswd and htdigest for basic/digest auth
auth-ldap libopenldap auth users against an ldap server
compress-bzip2 libbz2 optional, non-standard bzip2 compress for mod_compress
compress-deflate libz deflate compress for mod_compress
compress-gzip libz gzip compress for mod_compress
large-files libc/os large files support
network-ipv6 libc/os ipv6 support
network-openssl libopenssl ssl cabability
regex-conditionals libpcre =~ and !~ in config conditionals
stat-cache-fam libfam/gamin caches stat() calls with the help of FAM
storage-gdbm libgdbm local, non-cluster storage for mod_trigger_b4_dl
storage-memcache libmemcached distributed storage for mod_trigger_b4_dl
webdav-locks libxml2, sqlite3, libuuid file locking for mod_webdav
webdav-properties libxml2, sqlite3 property storage for mod_webdav