Dead link, simply means that the link of the website can not be accessed normally, there are many reasons for dead link, such as the link destination page has been deleted or transferred; Site move results in invalid link; Setting a static link makes the original chapter link address inaccessible. Export link changes, etc. If the website has a large number of dead links that can not be accessed, it will first affect the user's visit mood, followed by the impact of the website in the search engine weight, think about the crawler in the crawling process to overgrown weeds, dead roads, what will be the feeling ah. Therefore, from time to time to detect the website dead links and then delete or reset it is necessary, the following summary of several websites dead link detection and query tools, help the website dead link check, improve the website user experience and enhance the website weight. Note that some tools are wall site links are also considered dead links, these wall and inaccessible links may be temporary or long-term, retain or delete their own decision