Why broken links matter
A broken link is a dead end for a reader and a wasted path for a crawler. A few are normal on an older page; many make a site look abandoned and waste the link value you pass.
Links that redirect still work, but pointing at the final URL is faster and cleaner, especially for your own internal links.
Questions
How many links does it check?
Up to 40 per page, internal and external, in the order they appear.
Why is a working link marked as blocked?
Some sites refuse automated requests with 403 or 429. Open those links yourself to confirm.
Does it crawl my whole site?
No, one page at a time. Run it on the pages with the most links.
Are mailto and tel links checked?
No, only http and https links.