Google recently updated it's Webmaster Tools, and Vanessa Fox (the original creator of Google Webmaster Tools) wasn't happy.
Among the updates in the Webmaster Tools system was a reduction in the number of errors a web designer or webmaster would receive from the application. The system will now only document up to 1000 errors from within the administrative portal of Webmaster Tools. However, using the GData API you can still receive up to 100,000 URLs for each error with programmatic access.
Two different types of files are available regarding crawl errors:
Crawl error data is essentially available in four ways:
In her article in Search Engine Land, Vanessa Fox elaborates on the specifics of each way of retrieving the crawl error data from the tool.
SOURCE: https://searchengineland.com/google-webmaster-tools-crawl-errors-how-to-get-detailed-data-from-the-api-115153