What is the primary purpose of implementing crawl-delay within the robots.txt file?

The primary purpose of implementing 'crawl-delay' within the robots.txt file is to manage the crawling rate of web crawlers, specifically Yandexbot, to prevent overloading a website's server. Crawl-delay instructs the crawler how many seconds to wait between successive requests. By setting an appropriate crawl-delay, website owners can ensure that Yandexbot does not make too many requests in a short period, which could strain server resources, slow down the website for users, or even cause temporary unavailability. For instance, a crawl-delay of '10' would instruct Yandexbot to wait 10 seconds between each page request. This is especially crucial for websites hosted on shared servers with limited resources, or those experiencing high traffic. An incorrectly configured crawl-delay, either too low or too high, can negatively impact a website's indexing: too low may overload the server, leading to incomplete crawling, while too high may slow down the rate at which new or updated content is indexed. It's essential to monitor server performance and adjust the crawl-delay accordingly to achieve a balance between efficient crawling and optimal website performance.