A variety of free tools exist that can assist you with finding broken links on your static website.
These three are the most popular:
Google Search Console:
If the Google crawler finds any 404 errors, they are displayed in Google Search Console, where they can also be marked as corrected. There are additional functions that enable you to detect errors in robots.txt files.
Dead Link Checker:
Using the Dead Link Checker, you can find both internally and externally linked 404 pages quickly and easily. All error pages tracked by the app are listed along with their status codes and URLs.
W3C Link Checker:
Just enter the URL into the W3C Link Checker, and it will provide you with a comprehensive report.
We can also provide real time access logs for your website for customers on an Enterprise plan, which can be used to check for any requests resulting in a 404.