Googlebot

What it is

Googlebot is the software Google uses to crawl the web: it requests your pages, follows links, and hands what it finds to the indexing pipeline. There are two crawlers. Googlebot Smartphone is the primary one, because Google is mostly mobile-first now, so it mainly sees your site as a phone would. Googlebot Desktop still exists for some checks. It crawls a typical site roughly once every few seconds on average, reads the first 2MB of an HTML page, and runs from US IP addresses on Pacific Time (per Google's Googlebot documentation).

Why it matters

If Googlebot cannot fetch and read a page, nothing else you do will rank it. Three things follow. First: build and test for mobile, since the Smartphone crawler is what counts. Second: put your important content and links in the first 2MB of HTML, not buried after megabytes of inline scripts. Third: do not accidentally block it. A robots.txt rule stops crawling; a noindex tag stops indexing. Plenty of bots also spoof Googlebot's user agent, so verify real ones by IP. To see how this fits the bigger picture, read how Google crawls, indexes, and ranks and our note on crawlability.