LinkChecker is a free, GPL licensed URL validator.
recursive and multithreaded checking
output in colored or normal text,
HTML, SQL, CSV, XML or a sitemap graph
in different formats
HTTP/1.1, HTTPS, FTP, mailto:, news:,
nntp:, Telnet and local file links
support
restriction of link checking with
regular expression filters for URLs
proxy support
username/password authorization for
HTTP and FTP and Telnet
honors robots.txt exclusion protocol
Cookie support
HTML and CSS syntax check
Antivirus check
a command line interface
a GUI client interface
a (Fast)CGI web interface (requires
HTTP server)