Links are a huge part of SEO. From backlinks helping establish your domain authority to internal links keeping visitors on your site. Among other things, Google scours links and determines your worthiness for the top of the SERPs. Check My Links Chrome Extension makes sure all your links are working.
Install the simple plugin and reveal working and non-working links on pages you visit. Use it to determine what needs fixing on your site. Or, use it to find opportunities where you can link back to yourself (i.e. Wikipedia) or offer one of your own links to content creators showing a broken link.