Googlebot is the crawler of Google Search. In its explanation of Googlebot, Google distinguishes Googlebot Smartphone, which behaves like a mobile visitor, and Googlebot Desktop. Most requests come from the mobile crawler, because Google mainly indexes the mobile version of pages. Both use the token Googlebot in robots.txt.
According to Google, blocking Googlebot affects Google Search, including Discover and all Google Search features.
Worth knowing
According to the same page, Googlebot crawls the first 2 MB of an HTML file or other supported file type. For PDFs, the limit is 64 MB. If important content only comes after that limit in the code, Google does not take it into account.
How do you check it?
Other bots often imitate Googlebot’s user agent. Google recommends verifying a request with a reverse DNS lookup of the IP address, or comparing the IP address with the lists Google publishes.
host <IP address from your server log>If the name returned does not belong to Google, or the IP address is not in Google’s lists, the visit did not come from Googlebot.
Common mistake
Using robots.txt to remove a page from Google. Google writes that a blocked URL can still appear in search results. If you do not want a page in Google, use noindex and keep the page crawlable.
More in Why is my page not showing in Google? and under mobile-first indexing.