What is Mobile-First Indexing?
Google primarily uses the mobile version of a page for indexing and ranking. Parity between mobile and desktop content, links, and metadata is therefore a baseline audit check.
Related terms
Crawling
How search-engine bots discover pages by following links, sitemaps, and directives. If a URL is never crawled, it cannot be indexed no matter how good its content is.
Indexing
Storing and organizing crawled pages so they can be retrieved for queries. Indexing is selective: crawled does not mean indexed, and indexed does not mean ranking.
Page Speed
How fast a page becomes usable, measured by field metrics like LCP and INP rather than single lab scores. Small gains compound commercially: a tenth of a second has moved retail conversions measurably.
Technical SEO
The crawling, indexing, rendering, and performance work that lets search engines reach, understand, and serve your pages. It covers directives, architecture, speed, and structured data rather than words on the page.
Crawl Budget
The number of pages a search engine will crawl on a site in a given period, driven by server capacity and demand signals. Large or slow sites must spend it on indexable, valuable URLs.
Robots.txt
A plain-text file at the domain root telling compliant crawlers which paths they may fetch. It controls crawling, not indexing: blocked URLs can still be indexed by URL if linked.