The checker tests every link on the WordPress post or page you enter above, up to 100 per run, then lists the broken ones first and the redirects after them. Nothing is installed on the site, so it also works on a site you cannot log into.
The Broken Link Checker plugin
Listed on WordPress.org, it scans a whole site: posts, pages, comments and custom fields. It can check from WPMU DEV's cloud or from your own server, and it is the one to install when you want the whole site watched.
Use the checker here when you want one page checked now, such as a post you have just updated or a page on a client's site.
What a run covers
- Every link on the one page you enter, up to 100. A page with more says how many were left out.
- Broken links first, such as 404s and domains that no longer exist, then redirects. It checks the one page and does not crawl the rest of the site.
This broken link checker is free with no signup. SearchBlueprint, who make it, sell SEO planning for websites: which searches each page should answer.